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I 

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WILSON'S  Photographics. 

(Ask  for  CHAUTAUQUA  EDITION.) 

The  best  photographic  lesson-book,  by  Edward  L.  Wilson,  editor  of  Wilson's 
Photographic  Magazine,  Photographic  Mosaics,  etc.  The  author  believes  it  to 
be  the  best  ellbrt  he  has  ever  made,  and  bogs  leave  to  call  attention  to  a  few 
of  its  peculiar  advantages  as,  a  standard  work  for  all  workers  in  photography . 

A.  Treatment  of  the  Subject;  B.  The  Needful  Apparatus;  C.  The  Objec- 
tive Or  Lens ;  D.  The  Dark-room  ;  E.  Preparation  of  the  Glass ;  F.  Chemicals 
and  Solutions;  G.  The  Manipulations:  H.  Manipulatory  Miseries;  I.  Re- 
touching the  Negative ;  J.  The  Glass  Studio  ;  K.  Accessories  and  Light :  L. 
Managing  the  Model ;  M.  Printing  on  Albumen  Paper;  N.  Printing  on  Plain 
Paper;  O.  General  Remarks  on  Printing;  P.  Printing  on  Various  Surfaces ; 
Q.  Printing  Perplexities ;  R.  Art  in  Printing;  S.  Mounting  and  Finishing; 
T.  Photography  Outside;  U.  Bromo-gelatine  Emulsion  Work;  V.  Vogers 
Collodion  Emulsion ;  W.  Enlargements  and  Lantern  Slides;  X.  Phototypes, 
Platinotypes,  and  Collodion  Transfers  ;  Y.  Wastes  and  their  Worth  ;  Z.  Met- 
rical Measuring ;  &.  Concluding  Confab ;  Index  (six  pages). 

It  is  believed  that  this  is  the  most  valuable  work  ever  offered  to  the  work- 
ing photographer.  It  contains  352  pages.  More  than  100  illustrations.  Com- 
panion to  Quarter  Century, 

$4.00  POST-PAID  $4.00. 

It  is  printed  on  fine  white  paper  made  especially  for  it.  The  author  has 
received  a  thousand  testimonials.  For  the  beginner,  for  the  amateur,  for  the 
photographic  worker,  it  is  believed  to  be  the  most  complete. 

EDWARD  L.  WILSON,  853  Broadway,  New  York. 


Wl  LSOIM'S 

QUARTER  CENTURY  IN  PHOTOGRAPHY 

Contents: — 1.  The  History  of  Photography  ;  2.  The  Theory  of  Photography ; 
3.  Light ;  4.  The  Camera  ;  5.  About  Lenses  ;  6.  The  Diaphragm,  or  Stop ;  7. 
Glass-house  Construction  ;  8.  Under  the  Skylight ;  9.  The  Application  of  Art 
Principles ;  10.  Outdoor  Operations  ;  11.  Exposure, "or  the  Question  of  Time  ; 
12.  Concerning  Chemicals ;  13.  Dark-room  Contrivances ;  14.  Negative  Making, 
Wet ;  15.  Negative  Making,  Dry ;  16.  Negative  Making,  Paper  and  Film ;  17. 
Retouching  and  Doctoring  the  Negative ;  18.  Printing  on  Albumenized  Paper ; 
19.  Printing  Drawbacks  and  Defects— Causes  and  Remedies ;  20.  Printing-room 
Particulars ;  21.  Peculiar  Printing  Processes ;  22.  Color-sensitive  Photography 
— Isochromatic— Orthochromatic ;  23.  Photo-engraving  and  Pictorial  Illus- 
trations ;  24.  Lantern  Slides  and  Transparencies. 

For  the  modern  student  this  is  the  best  book.  The  thorough  student  needs 
both.   Except  for  special  departments  of  work,  no  other  books  are  needed. 

Price,  $4.00  Post-paid. 

The  arrangement  of  Quarter  Century  is  exceptional  in  one  respect  that  greatly 
increases  its  value  for  general  work  :  The  main  text  is  supplemented  by  fo;>t 
notes  in  smaller  type,  comprising  quotations  from  all  our  leading  writers,  and 
in  many  cases  containing  original  methods  not  yet  generally  known  to 
photographers.  Its  readers  will  be  more  than  repaid  by  a  close  comparison  of 
the  methods  presented.— Ir on. 

The  great  test  of  such  a  book  comes  not  with  the  reading,  but  with  the  use. 
The  clear  style,  the  straightforward  directness  of  every  line,  the  exactness  of 
all  dimensions  given,  and  the  fulness  of  all  treatments,  give  assurance  that 
this  work  is  for  use.  We  do  not  see  how  any  photographer,  or  any  learner  of 
this  wonderful  art,  can  attain  the  most  complete  and  perfect  mastery  of  the 
subject  without  this  work.  It  is  a  complete  thesaurus,  and  one  not  soon  to  be 
supplanted  by  a  better.— Dean  Wright,  in  the  Boston  Academy. 

EDWARD  L.  WILSON,  853  Broadway,  New  York. 

(O 


THE  BEST  REAPERS  IN  THE  FIELD  OF  ART  HAVE  LEFT  FOR  US 
THE  WINNOWED  GRAIN,  IN 

JOHN  BURNET'S  "ART  ESSAYS." 

COMPOSITION,         LIGHT  AND  SHADE, 
EDUCATION  OF  THE  EYE. 

Fac-simile  Photo-lithographic  Reproduction  of  Three  Works  in  One 
from  the  (1822-1827)  Originals. 

This  work  should  be  in  the  hands  of  every  one  who  would  understand  the  prin- 
ciples of  art.  It  teaches  every  one,  from  the  rudiments  to  the  highest  forms  of 
composition.  Photographer  and  painter  alike  will  find  it  invaluable.  One 
hundred  and  forty  fine  illustrations  and  etchings  (some  of  them  full  page)  are 
given  from  the  most  exemplary  works  of  Cuyp ;  Potter ;  Ostade ;  Burnet ; 
Claude ;  Rubens  ;  De  Laer ;  Terburg ;  Metzu  ;  Rembrandt ;  Corregio ;  Raphael ; 
Guido ;  West ;  Domenichino ;  Wilkie  ;  and  others. 

For  twenty  years  it  has  been  my  personal  Art  Text-book.  It  is  invaluable, 
and  I  give  it  the  highest  commendation.  Edward  L.  Wilson. 

If  photographers  really  cared  for  art,  which  I  sometimes  doubt,  and  knew 
the  value  of  these  books,  you  would  sell  a  large  edition.     H.  P.  Robinson. 

The  " Practical  Essays  of  Art"  form  the  safest  guide  to  all  students  of  pic- 
torial arrangement  and  composition.  It  is  not  a  book  to  be  placed  on  the 
library  shelves  to  be  consulted  from  time  to  time,  but  rather  one  to  be  studied 
daily  until  all  the  principles  it  advances  have  become  a  part  of  one's  definite 
knowledge.   Delight  in  possession  of  this  sort  no  money  can  express. 

J.  Wells  Champney. 

You  certainly  deserve  great  credit  for  resurrecting  this  valuable  and  much 
needed  Avork,  and  success  is  sure  to  come.  Enoch  Root. 

Mr.  Wilson  has  rendered  a  service  to  artists,  amateurs,  and  students,  by  the 
republication  of  these  essays  of  the  late  John  Burnet,  which  have  been  long 
out  of  print,  and  difficult  to  procure  in  their  original  form.  He  has  availed 
himself  of  the  new  art  of  reproduction  by  photography,  and  by  its  aid  has 
put  the  original  book  before  us  in  fac-simile— type  and  illustrations  alike,  and 
in  the  same  form  in  which  it  was  published — a  convenient  small  quarto,  with 
a  well-opened  page  and  ample  margins :  a  form,  it  may  be  added,  much 
affected  in  the  first  quarter  of  the  century. — The  Studio. 

From  "  Iron." 

The  publication  of  these  reproductions  will  be  hailed  with  great  pleasure 
by  all  students  of  art,  and  particularly  by  artistic  photographers. 

From  the  66  London  Camera." 
Dr.  Wilson  has  hit  upon  the  very  happy  idea  of  reproducing  these  three 
valuable  works  bound  into  one  volume— with  all  the  original  illustrations. 
The  book,  indeed,  is  a  fac  simile  reproduction  of  the  originals,  both  pictures 
and  text  being  copied  by  the  aid  of  photo-lithography. 

From  the  "  St.  Louis  Photographer." 
While  all  parts  are  of  great  value  to  the  student,  we  think  the  part  on 
"  Education  of  the  Eye  "  will  be  found  of  most  practical  value  to  the  photog- 
rapher, as  that  organ  is  very  deficient,  and  much  in  need  of  education. 

Photographers  and  all  other  artists  owe  you  a  debt  of  gratitude  for  giving 
them  the  opportunity  of  becoming  possessors  of  such  a  work. 

Prof.  C.  H.  Bothamley. 

It  is  handsomely  bound.  $100  cannot  purchase  a  copy  of  the  original  work. 
Price,  POST-PAID,  $4.00,  to  any  country. 

E.  L.  WILSON,  Photo.  Pub.,  853  Broadway,  N.  Y. 


A  NEW  BOOK. 


ALL  SECRETS  OPENED, 


PHOTO-ENGRAVING,  PHOTO-ETCHING, 
and  PHOTO-LITHOGRAPHY. 

C"  OMPLETE  instructions  and  formulae  by  an  expert  in  England  (W.  T. 
Wilkinson),  with  my  own  contributions  and  translations  from  the  French 
and  German.      The  whole  of  the  Processes  made  known. 
CONTENTS. 
PART  I— PHOTO-ENGRAVING  IN  LINE. 
Chapter  I— Appliances  for  Making  Photographic  Negatives.    II— The  Wet 
Collodion  Process.   Ill— Photographic  Manipulations.   IV— Apparatus  for 
Printing  Upon  Zinc.   V — Printing  on  Zinc  in  Albumen.   VI— Printing  on 
Zinc  in  Bitumen.   VII— Direct  Transfers  to  Zinc.   VIII— Etching  Line 
Transfers. 

PART  II— PHOTO-ENGRAVING  IN  HALF-TONE. 
Chapter  I— Retrospective.    II — Making  Grained  Negatives.    Ill— Etching 
in  Half-tone.    IV — Printing  from  the  Block.    V— The  Transfer  of  the 
Drawing  and  its  Treatment  before  Etching.   VI — Hints  from  all  Sources. 
PART  III— PHOTO-ENGRAVING  ON  COPPER. 
Chapter  I— Subjects  in  Line.   II   Half-tone  Intaglios.   Ill— Half-tone  In- 
taglios— Continued.   IV— Half-tone  Intaglios,  Electro  Method. 

PART  IV— PHOTO-LITHOGRAPHY  IN  LINE. 
Chapter  I— Photo-lithography  in  Line.    II — Paper  Transfers.    Ill— Paper 
Transfers — Continued.    IV-  Toovey's  Negative  Transfer  Process.    V — To 
Develop  Photo-litho.  Transfers. 

PART  V— PHOTO-LITHOGRAPHY  IN  HALF-TONE. 
Chapter  I— Photo-lithography  in  Half-tone.    II— Ink  Photos.    Ill— Hus- 
band's Papyrotint  Process. 

PART  VI— COLLOGRAPHIC  PRINTING. 
Chapter  I— Half-tone  Photographic  Negative.   II— The  Heliotype  Process. 
Ill— The  Collotype  Process.   IV— Printing  from  the  Collotype  Plate.  V— 
The  New  Home  Printing  Process. 


It  describes  graphically  and  in  a  comprehensive  manner,  and  supplies  a 
long-felt  want.— Photo.  Times. 
We  heartily  commend  a  book  that  is  so  well  made.— Anthony's  Bulletin. 
The  knowledge  of  the  subjects  treated  is  becoming  more  and  more  a 
necessity. — The  St.  Louis  and  Canadian  Photographer. 

180  pages  6#  x  8%  in.  Cloth  Bound,  Price  $3.00,  Post-paid. 
Many  illustrations  and  a  complete  index. 


Edw.  L.  Wilson,  Photo-Book  Publisher, 
No.  853  Broadway,  New  York. 


The  Photographic  Times, 

Edited  by  W.  I.  LINCOLN  ADAMS, 

Is  Illustrated  Every  Week  with,  a  Full-page  Picture, 

thus  including  in  the  year  FIFTY-TWO  FULL-PAGE  PICTURES,  and 
making  it  the  best  illustrated  Photographic  periodical  in  the  world.  Special 
numbers  contain  more  than  one  high-grade  illustration ;  and  there  are  pub- 
lished, beside  these,  superb  Photogravures,  pictorial  illustrations,  by 
other  photographic  and  photo-mechanical  printing  processes. 

The  illustrations  are  carefully  selected,  and  represent  the  best  work  of 
representative  American  artists.  There  are  also  copies  of  famous  pictures, 
from  time  to  time,  to  illustrate  lessons  in  art  for  photographers,  accompanied 
by  instructive  reading  matter. 

The  Editorials  and  Editorial  Xotes  are  of  greatest  practical  value, 
as  they  are  the  result  of  actual  practice  and  experiment,  by  the  staff. 

Leading  Articles  by  such  acknowledged  authorities  as  Prof  W.  K. 
BURTON,  on  Scientific  and  Practical  Subjects  ;  ANDREW  PftlN- 
GLE,  on  Subjects  of  Greatest  Value;  P.  C.  DUOHOCHOIS,  on 
Chemical  Subjects;  W.  J.  STILLMAN,  on  Art  and  Practical  Subjects  ; 
Prof.  CHARLES  EHRMANN,  on  Dark-room  and  Printing  Prac- 
tices; and  frequent  contributions  from  G.  Watmough  Webster,  F.C.S.,  of 
England;  Carl  Srna,  Charles  Scolik,  Dr.  Eder,  Prof.  Spitaler,  Lieut.-Col. 
Volkmer,  of  Austria ;  Dr.  Lohse,  Dr.  Schnauss,  Karl  Schwien,  Victor 
Schuman,  and  F.  Mueller,  of  Germany. 

Notes  from  the  Every-day  Gallery  Experiences  of  such  well-known 
Practical  Photographers  as  W.  H.  siJerman,  Prof.  Karl  Klauser,  J.  M. 
Mora,  H.  McMichael,  J.  R.  Swain,  and  John  Carbutt. 

Various  Occasional  Articles  of  a  Practical  Nature,  and  otherwise,  by  our 
favorite  contributors:  Rev.  C.  E.  Woodman,  Ph.D.,  C.  D.  Cheney,  D.D.S., 
Henry  M.  Parkhurst,  Charles  Wager  Hull,  C.  W.  Canfield,  Rev.  G.  M. 
Searle,  Miss  Frances  B.  James,  C.  M.  Brockway,  Miss  Adelaide  Skeel.  A 
highly  valuable  series  of  Papers  on 

THE  PHOTO-MECHANICAL  PRINTING  PROCESSES, 

By  Ernest  Edwards,  president  of  the  Photo-gravure  Company. 

"Pictures  of  the  Month,"  and  the  series  of  practical  "  Chips  from  an 
Amateur's  Workshop,"  by  the  Rev.  W.  H.  Burbank.  "Occasional 
Notes,"  by  Prof.  W.  H.  Pickering,  of  Harvard  College  Observatory.  The 
Chemistry  of  Photography,  by  Jerome  Harrison,  F.G.S. 

Correspondence.-  Scientific  and  practical  discussion  of  important  and 
interesting  questions,  by  practical  photographers,  and  letters  from  all  parts 
of  the  globe,  by  intelligent  and  observing  correspondents.  Notes  and 
News,  Photographic  Societies,  The  Chautauqua  School  of 
Photography,  Queries  and  Answers,  Our  Editorial  Table, 
Record  of  Photographic  Patents  and  Commercial  Intelligence 
will  be  maintained  and  improved  under  the  Separate  Departments,  which 
have  proved  so  popular  to  our  readers  heretofore. 

One  Year,      -      $5.00.  \  Six  Months,      -  $2.50. 
One  Month's  Trial,      -  50e. 
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THE  PHOTOGRAPHIC  TIMES  FUB'ft  ASSOCIATION,  Piliste, 

4:23  Broome  Street,  New  York  City. 


The  Kodak  Camera. 

This  wonderful  little  instrument  supplies 
the  means  for  the  practice  of  that  most  fasci- 
nating pastime — Amateur  Photography — in  a 
manner  so  simple  that  all  may  enjoy  it.  The 
Kodak  may  be  used  by  anybody  who  can 
press  a  button,  this  comprising  the  operation 
of  making  a  picture.  One  hundred  instanta- 
neous views  are  taken  without  re-loading,  and 
the  camera  is  always  ready  for  use.  After  the 
PRICE,  $25.00.  exposures  have  been  made,  the  camera  can  be 
sent  to  the  factory,  where  the  pictures  are  developed  and  finished,  and 
a  fresh  spool  of  sensitive  film — material  for  another  hundred  pictures 
— inserted.  If  desired,  however,  the  amateur  can  finish  his  own 
pictures. 

The  Kodak  is  invaluable  for  tourists,  yachtmen,  wheelmen,  or  for  anybody  who 
wishes  to  obtain  an  accurate  illustrated  record  of  the  many  interesting  sights  and 
incidents  of  a  journey,  or  of  every  day  happenings.  Send  for  a  copy  of  the  Kodak 
Primer,  with  sample  photograph. 

Good  Lantern  Slides  can  be  made  from  KODAK  Negatives. 

The  Kodak  is  for  sale  by  all  Photo  Stock-dealers. 


EASTMAN'S  PERMANENT  BROMIDE 

Transparency  Plates 

for  Lantern  Slides,  are  in  use  by  the  principal  amateurs  throughout  the 
country.  Being  very  large  manufacturers  of  emulsions  for  positive 
printing,  we  are  enabled  to  select  emulsions  for  our  lantern  plates  that 
give  the  exact  tone  required.  A  uniformity  is  thus  secured  which  can 
be  obtained  in  no  other  plates. 

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5    x  8    1  75 

6K  x  sy2   2  30 

8    x  10   3  40 

10    x  12   5  00 


For  sale  by  all  Photo  Stock-dealers. 


THE  EASTMAN  DRY  PLATE  AND  FILM  CO. 


Branch  Office, 
115  Oxford  St,,  London. 


ROCHESTER,  N.  Y. 


Roberts  &  j^ellows, 

(Suocessors  to  EDWAKD  L,  WILSON.) 

PUBLISHERS  OF  CHOICE 

FOREIGN  a  AMERICAN  PHOTOGRAPHS 


MANUFACTURERS  AND  DEALERS  IN 

PkoloppMc  Transparencies  for  the  Optical  Lantern. 


AGENTS  FOR  THE 

-wSMelNTOSH^w- 

STEREOPTICONS,  SCIOPTICONS, «  MICROSCOPES. 


Views  for  the  Lantern,  for  Instruction 
and  Amusement,  in  great  variety. 

Slides  made  to  order,  for  Lecturers,  Ex- 
hibitors, Amateurs  and  others. 

Artistic  Lantern  Slide  Coloring  made  a 
Specialty. 

1305  Arch  Street  PHILADELPHIA,  PA. 

Send  for  Catalogue. 


TOILERS  OF  THE  THAMES 

i  Lcuitern  Slide,  by  the  Author. 


T  H  E 


BOOK  OF  THE  LANTERN. 

BEING  A 

PRACTICAL  GUIDE  TO  THE  WORKING  OF  THE 
OPTICAL  (OR  MAGIC)  LANTERN. 

WITH  FULL  AND  PRECISE  DIRECTIONS  FOR  MAKING  AND 
COLORING  LANTERN  PICTURES. 


WITH  SEVENTY-FIVE  ILLUSTRATIONS. 


BY 


T.  C.  HEPWORTH,  F.C.S., 

FOR  MANY  YEARS  LECTURER  TO  THE  ROYAL  POLYTECHNIC  INSTITUTION,   LONDON  ; 
LECTURER  ON  PHOTOGRAPHY  AT  THE  BIRKBECK  INSTITUTION  J  AND 
EDITOR  OF  "THE  CAMERA." 


First  American  from  the  Second  English  Edition. 


NEW  YORK: 
EDWARD  L.  WILSON, 
853  Broadway. 

1  88  9. 


Entered,  according  to  Act  of*  Congress,  in  the  year  1889, 
By  EDWARD  L.  WILSON, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D. 


CONTENTS. 


Chapter  Page 

I. — The  Construction  of  the  Lantern          BP  1 

II. — The  Optical  System  of  the  Lantern       •      .  .16 

III.  — Oxygen  Gap.  Making   30 

IV.  — Limelight  Jets,  Regulators,  Pressure  Boards,  <ic.  .  50 
V. — The  Limelight  and  its  Management       .      .  .71 

VI.— Screens   86 

VII. — The  Preparation  of  Lantern  Slides,  Diagrams,  &c, 

without  the  aid  of  Photography  .       .       .  .97 

VIII. — Lantern  Slide  Making  by  the  Wet  (Photographic) 

Process      .   104 

IX. — Lanterh  Slides  on  Dry  Plates      ♦      ,       #  .109 

X. — Home-made  Gelatine  Plates  .      ,      ♦      .  .125 


Vi  CONTENTS. 

XI. — On  Colouring    Photographic  Transparencies  for 

Lantern  Slides  •  .145 

XII.  — The  same  subject  continued  .       •      •      #  . 

XIII.  — Description  of  various    Experiments — Chemical, 

Electrical,  &c. — for  Class  Instruction,  which  are 
possible  with  the  Lantern  171 

XIV.  — The  Lantern  as  an  Aid  to  the  Photographer  .       .  204 
XV.— The  Art  of  Making  Photo-Micrographs  .  .211 

XVI. — Enlarging  Photographs  with  the  Lantern  222 

XVII. — The  Lantern  Microscope  and  the  Opaque  Lantern  .  240 

XVIII. — Various  Lantern  Accessories  .       .       .  250 

XIX. — Practical  Hints  to  those  who  Employ  the  Lantern 
for  Scientific  Demonstration  or  for  Entertain- 
ments in  the  Drawing  Room  or  Lecture  Hall  264 


PREFACE. 


S  it  is  customary  for  an  author  to  say  a  few 
words  to  his  readers  by  way  of  introduction, 
before  they  become  better  acquainted  with 
one  another,  let  me  briefly  state  the  reason  why 
this  book  is  written,  and  why  I  felt  some  confidence 
in  undertaking  the  work.  The  magic  lantern  has 
always  been  one  of  the  most  popular  instruments 
ever  made.  So  popular  has  it  been,  that  children  by 
the  thousand  recognise  its  charms,  while  many  of  more 
mature  years  have  a  secret  hankering  after  it,  which 
they  would  fain  leave  unacknowledged  :  u  For  it  is  but  a 
toy,"  think  they,  "and  we  have  left  toyland  behind 
us  since  we  reached  man's  estate."  Let  me 
sympathise  with  these  feelings,  and  own  for  my  pai-t 
a  weakness  for  pantomimes  and  fireworks,  which 
weakness  I  have  occasionally  the  opportunity  of 
indulging,  on  the  plea  of  taking  my  children  out  for 
a  treat.    But  let  me  say  at  once  that  the  magic  lantern 


viii 


PREFACE. 


is  now  no  toy,  but  is  recognised  as  a  valuable  aid  to 
education  far  and  wide.  The  reason  for  this  is  not 
far  to  seek.  First,  we  have  to  look  at  the  vast 
improvement  in  the  instrument  itself.  So  long  as  the 
greasy,  evil-smelling  oil  lamp  was  almost  the  sole 
illuminant  available,  and  roughly  executed  daubs  in 
varnish  colours  on  glass  the  only  works  of  art  (?) 
which  could  be  purchased  for  the  lantern,  it  did  not  much 
signify  that  the  lenses  were  also  of  a  faulty  character, 
and  no  better  in  quality  than  the  "  bull's  eye"  of  the 
nocturnal  policeman.  But  when  the  brilliant  limelight 
came  to  be  adapted  to  the  lantern,  it  was  at  once  seen 
that  the  capabilities  of  the  instrument  were  not  only 
much  increased,  but  almost  without  limit.  It  would 
be  difficult  to  say  offhand  how  many  persons  visited 
the  Royal  Polytechnic  Institution  in  the  forty  years 
during  which  it  was  open  to  the  public ;  but  it  is 
within  my  own  experience  that  at  one  period,  at  the 
time  of  the  "  ghost "  illusion,  they  came  at 
the  rate  of  two  thousand  per  diem.  There  is  no 
doubt  whatever  that  the  Polytechnic  caused  this  form 
of  amusement  to  become  popular,  for  the  lecturers 
affiliated  to  the  Institution  travelled  the  country 
round,  and  gave  similar  entertainments  in  all  parts. 

There  are  few  branches  of  science  in  which  the 
optical  lantern  cannot  be  made  useful  for  purposes  of 
demonstration,  and  as  this  fact  becomes  better  known, 
every  schoolroom  in  the  kingdom  will  be  provided 
with  one.    In  every  lecture  theatre  worthy  of  the 


PREFACE. 


IX 


name  the  instrument  is  already  constantly  called  upon 
to  illustrate  various  subjects,  and  I  venture  to  state 
that  its  use  will  be  greatly  increased  now  that  so 
much  attention  is  being  paid  to  the  art  of  photo- 
micrography, by  which  enlarged  pictures  of  micro- 
scopic objects  can  be  easily  rendered  available  for 
projection  by  means  of  the  lantern.  A  large  class 
of  students  can  thus  at  the  same  moment  study  the 
structure  of  an  organism  which  may  be  in  reality 
invisible  to  unaided  sight  by  reason  of  its  minute 
size. 

But  during  the  past  few  years,  the  number  of  those 
who  interest  themselves  in  the  lantern  and  its 
capabilities  has  been  vastly  increased  by  the  sudden 
popularity  of  the  art  of  photography.  Amateur 
photographers  are  now  to  be  found  in  every  town  in 
the  kingdom,  and  they  are  beginning  to  find  out  that 
there  is  no  better,  method  of  showing  their  friends  the 
pictures  which  they  have  taken  than  by  means  of  the 
optical  lantern.  The  same  instrument,  too,  as  it 
offers  a  means  of  making  permanent  enlarged  copies 
of  small  photographs,  serves  with  them  a  double 
purpose. 

The  introduction  as  illuminants  of  the  hydrocar- 
bons, under  the  name  of  petroleum,  parnffin,  kerosene, 
&c,  has  also  had  its  share  in  the  recent  development 
of  the  optical  lantern,  for  now  a  few  pounds  will 
purchase  a  better  instrument  than  was  procurable  at 
any  price  twenty  years  ago. 

b 


X 


PREFACE. 


With  these  facts  in  view,  I  have  long  thought  that 
a  thorough  guide  to  the  working  of  the  optical  lantern, 
the  preparation  of  its  diagrams  and  pictures,  the 
colouring  of  the  same,  the  production  of  photo- 
micrographs, and  everything  pertaining  to  lantern 
work,  would  fill  a  vacant  place  in  technical  literature. 
Beyond  the  two  or  three  shilling  handbooks  which 
have  appeared,  there  is  nothing  of  the  kind  procurable; 
and  in  the  space  available  in  such  books,  it  is  obvious 
that  the  various  matters  to  which  I  have  referred 
cannot  be  sufficiently  dealt  with. 

Some  of  the  matter  here  printed  has  already 
appeared  in  The  Amateur  Photographer,  and  in  The 
Camera.  The  author  is  indebted  to  the  proprietors  of 
both  those  periodicals  for  their  courtesy  in  allowing 
both  text  and  cuts  to  be  reproduced  in  this  work. 


T.  C.  HEPWORTH. 


45,  St.  Augustine's  Road,  Camden  Square, 
London,  N.W. 

January ,  1889. 


CHAPTER  L 


m 


THE  CONSTRUCTION  OF  THE  LANTERN. 

KN"  that  wonderful  autobiography  of  Benvenuto 
Cellini,  which  Horace  Walpole  described  as 
being  "  more  amusing  than  any  novel,"  we 
find  the  account  of  a  weird  incantation  scene  which 
took  place  in  the  Colosseum  at  Rome.  Cellini  tells  us 
that  he  had  made  the  acquaintance  of  a  Sicilian  priest 
who  volunteered  to  initiate  him  into  some  of  the 
secrets  of  necromancy.  A  meeting  was  appointed  at  the 
Colosseum,  where  "  the  priest,  having  arrayed  himself  in 
necromancer's  robes,  began  to  describe  circles  on  the  earth 
with  the  finest  ceremonies  that  can  be  imagined.  I  must 
say  that  he  made  us  bring  precious  perfumes  and  fire,  and 
also  drugs  of  fetid  odour.  When  the  preliminaries  were 
completed,  he  made  the  entrance  into  the  circle ;  and 
taking  us  by  the  hand,  introduced  us  one  by  one  inside  it. 
Then  he  assigned  our  several  functions  :  to  the  necromancer, 
his  comrade,  he  gave  the  pentacle  to  hold ;  the  other  two 
of  us  had  to  look  after  the  fire  and  the  perfumes  ;  and 
then  he  began  his  incantations.    This  lasted  more  than  an 

B 


2 


THE  BOOK  OF  THE  LANTERN. 


hoar  and  a  half,  when  several  legions  appeared,  and  the 
Colosseum  was  all  full  of  devils."  It  has  been  suggested 
that  these  effects  were  produced  by  some  form  of  lantern 
casting  images  on  the  smoke  from  the  burning  drugs. 
Should  this  surmise  be  correct,  it  would  refer  the  use  of 
the  instrument  back  to  the  early  half  of  the  sixteenth 
century — Cellini  having  been  born  at  Florence  in  the 
year  1500 — and  the  event  spoken  of  having  occurred  in 
his  early  manhood. 

But  on  careful  perusal  of  the  entire  account  of  these 
supernatural  wonders,  I  feel  convinced  that  no  kind  of 
optical  instrument  can  have  been  used.  To  produce  any 
remarkable  effect  in  such  a  large  space  as  that  covered  by 
Vespasian's  Amphitheatre  would  certainly  tax  the  powers 
of  the  best  modern  lantern.  Besides  which,  Cellini  was 
a  remarkably  clever   and   observant   man,   and  would 


Fig.  1. 

probably  have  detected  the  employment  of  any  such 
apparatus.  It  is  far  more  probable  that  the  priest  was 
aided  by  a  number  of  confederates,  and  that  these  were  in 


THE  BOOK  OF  THE  LANTERN. 


3 


reality  the  legions  of  devils  which  so  impressed  the  super- 
stitions mind  of  the  Florentine  goldsmith  and  sculptor. 
With  far  more  reason  might  we  suspect  the  use  of  the 
lantern  in  those  manifestations  which  are  said  to  take 
place  among  the  so-called  spiritualists  and  their  mediums 
of  to-day. 

We  are  certainly  on  much  firmer  ground  when  we 
ascribe  the  first  conception  of  the  instrument  to  Athanasius 
Kircher,  the  learned  Jesuit  of  the  seventeenth  century, 
who  has  left  so  many  volumes  to  testify  to  the  great  gifts 
which  he  possessed.  For  in  one  of  these  books,  Ars  Magna 
Lucis  et  Umbrce,  we  not  only  find  descriptions  and  dia- 
grams of  numerous  optical  contrivances  (I  may  note  in 
passing  that  many  of  these  drawings,  redressed  and 
elaborated,  appear  in  modern  text-books  as  new  ideas), 
but  several  which  show  that  Kircher  quite  understood  the 
main  principle  upon  which  the  optical  lantern  depends. 
A  tracing  of  one  of  these  rude  cuts  is  given  at  fig.  1, 
from  which  it  will  be  seen  that  the  design  to  be  projected 
by  the  lens  is  illuminated  by  three  candles — the  brightest 
form  of  artificial  light  then  known — and  an  inverted 
image  is  thrown  upon  a  screen  at  a  distance. 

Here  we  have  practically  the  germ  of  the  aphengescope, 
or  opaque  form  of  lantern.  But  modern  writers  on  the 
subject,  in  referring  to  Kircher,  have  curiously  overlooked 
this  most  suggestive  drawing,  and  have  given  another  one 
from  his  book,  which  they  erroneously  describe  as  the  first 
form  of  magic  lantern.  This  I  also  reproduce  (see  fig.  2). 
The  description  appended  to  the  cut  certainly  does  not 
bear  out  that  view,  but  points  rather  to  a  means  of  in- 

B2 


4 


THE  BOOK  OF  THE  LANTERN. 


creasing  the  light  from  *any  lantern  by  using  a  parabolic 
reflector  behind  the  lamp  or  candle  flame.  The  passage 
(translated)  runs  as  follows  : — 

"  To  construct  an  ingenious  lantern  which  may  show 
things  written  at  a  great  distance  so  that  they  can  be 
read — 

"  Let  a  lantern  be  made  of  the  same  cylindrical  figure 


C 


as  you  see  here  represented,  in  whose  base  let  a  concave 
mirror  be  placed,  having  as  parabolic  a  shape  as  is  possible. 
Within  the  focus  of  this  mirror  let  F,  the  flame  of  a 
candle,  be  fixed,  and  you  will  have  what  is  required,  for 
it  will  shine  with  such  unwonted  splendour  as  to  show  by 
night,  without  any  trouble,  even  the  smallest  letters  when 
examined  by  the  aid  of  a  telescope.  But  persons  looking 
at  the  flame  from  a  distance  will  think  that  it  is  a  great 
fire.  If  the  inner  sides  of  the  cylinder  are  fashioned  of 
polished  tin  in  the  form  of  an  ellipse,  they  will  increase 
the  light.    But  the  figure  here  given  will  sufficiently  show 


THE  BOOK  OF  THE  LANTERN. 


5 


the  invention.  E  marks  the  handle  and  the  opening  (or 
window) ;  C  the  chimney  or  funnel." 

It  is  worthy  of  note  that  Sir  David  Brewster,  in  his 
"  Natural  Magic,"  quotes  the  incantation  scene  from 
Cellini  at  length,  and  states  his  conviction  that  the 
appearances  were  brought  about  by  optical  apparatus, 
although  he  admits  that  little  was  known  of  the  action  of 
mirrors  and  lenses  until  the  time  of  Kircher. 

It  is  obvious,  however,  that  such  primitive  instruments 
were  of  the  crudest  kind,  and  can  only  be  regarded  as 
interesting  curiosities.  Up  to  within  quite  recent  times 
lanterns  for  projection  held  about  the  same  relation  to  the 
modern  instrument  as  does  the  bone  needle  of  the  cave 
men  to  the  sewing  machine.  Like  most  instruments  of 
precision,  the  optical  lantern  is  the  outcome  of  many  years 
of  patient  thought  and  labour,  and  is  the  result  of  the 
working  of  many  minds.  No  individual  can  be  credited 
with  its  invention  or  discovery.  The  crude  idea  is,  as  we 
have  seen,  to  be  found  in  Kircher's  book,  and  one  improve- 
ment has  been  suggested  here,  and  another  there,  until  we 
have  before  us  a  very  perfect  optical  appliance. 

The  gradual  advance  in  the  instrument  very  naturally 
follows  the  introduction  of  improved  illuminants  for  more 
general  purposes.  The  oil  lamp  was  superseded  by  the 
argand  gas-burner,  and  this  was  in  its  turn  supplanted  by 
the  whiter  and  better  light  afforded  by  mineral  oil,  while 
before  this,  for  the  better  kind  of  lanterns,  Lieutenant 
Drrmmond's  brilliant  limelight  was  quickly  adopted  as  the 
best  for  the  purpose.  This,  too,  may  possibly,  in  the  near 
future,  give  way  to  the  still  more  brilliant  electric  arc 


6 


THE  BOOK  OF  THE  LANTERN. 


light.  But  the  introduction  of  mineral  oil,  in  conjunction 
with  the  adaptation  of  photography  to  lantern  pictures, 
have  been  the  main  factors  in  giving  the  instrument  its 
present  popularity. 

The  first  lantern  burning  mineral  oil,  and  called  the 
Sciopticon,  came  to  us  from  America.  It  was  constructed 
on  scientific  principles,  and  was  far  in  advance  of  anything 
of  the  kind  before  produced.  Tt  possessed  good  lenses 
and  a  powerful  lamp,  the  two  broad  wicks  of  which  were 
placed  edgeways  towards  the  condenser.  The  lamp  was  so 
closed  in  that  it  formed  a  combustion  chamber,  and  burnt 
the  oil  under  the  best  conditions.    The  lantern,  however, 


Fig.  3. 


had  its  faults.  The  front  glass  of  the  lamp  was  apt  to 
break,  and  a  dark  vertical  line  was  always  seen  upon  the 
sheet — a  line  which  was  in  reality  the  image  of  the  dark 
space  between  the  two  wicks.  By  adding  a  central  wick, 
and  by  making  certain  alterations  in  the  ventilation  of  the 
lamp  chamber,  Messrs.  Newton  conquered  both  these 
difficulties,  and  a  far  more  perfect  form  of  lantern  has 


THE  BOOK  OF  THE  LANTERN. 


7 


been  the  result.  The  same  makers  have,  too,  made  the 
lamp  distinct  and  separate  from  the  lantern,,  so  that,  if 
required,  it  can  readily  be  removed,  and  a  lime-jet  used 
in  its  stead.  The  form  of  lamp  referred  to  is  shown  in 
fig.  3,  both  open  for  trimming  and  closed  as  in  use, 
while  a  complete  mineral  oil  lantern,  of  the  kind 
now  adopted  by  most  makers,  is  seen  at  fig.  4.  The 


Fig.  4. 


management  of  oil  lanterns  is  so  simple,  really  resolving 
itself  into  the  necessity  for  keeping  the  burning  wicks  at 
a  correct  height,  and  putting  the  slides  or  pictures  on  the 
stage  provided  for  them,  that  no  more  space  need  be 
devoted  to  this  portion  of  my  subject. 

The  great  advantage  of  using  a  pair  of  lanterns  is  that 
whilst  a  picture  is  being  shown  by  one,  another  picture  is 
being  made  ready  in  the  other,  and  there  is  no  pause  or 
blank  screen  when  the  change  is  made.  The  so-called  dis- 
solving views,  which  are  produced  by  making  this  change 
slowly,  made  a  great  sensation  when  they  were  first  intro- 


8 


THE  BOOK  OF  THE  LANTERN. 


duced,  perhaps  because  few  knew  exactly  how  they  were 
managed.  But  they  are  now  so  common  that  many 
persons  consider  them  rather  tiresome  than  otherwise. 
Still,  they  give  the  operator  a  ready  means  of  varying  his 
work,  if  the  dissolving  apparatus  be  used  with  judgment. 
Thus  most  beautiful  effects  can  be  obtained  in  landscapes, 
more  especially  in  seascapes,  by  using  photographic 
cloud  pictures,  the  gradual  blending  of  one  clouded  sky 
into  another  giving  fine  aerial  and  very  natural  results. 
In  one  set  of  pictures  which  I  prepared  to  demonstrate 
the  beauties  of  cloudland,  in  connexion  with  a  lecture  on 


Fig.  5. 


ballooning,  a  sunrise  picture  was  made  to  melt  into  a  sun- 
set picture,  and  in  due  time  this  latter  gave  place  to  a 
moonlight  effect.  I  am  convinced  that  much  can  be  done 
in  this  direction  if  time  can  be  given  to  the  preparation  of 
the  pictures. 


THE  BOOK  OF  THE  LANTERN. 


9 


Originally  for  such  effects  two  separate  lanterns  were 
used  side  by  side,  but  now  a  biunial  lantern,  with  one 
optical  system  above  the  other,  is  employed  (see  fig.  5). 
The  modern  arrangement  is  far  more  convenient  for  the 
operator,  for  the  apparatus  is  compact  and  every  adjustment 
is  within  easy  reach  of  his  hand.  A  lantern  so  constructed 
generally  consists  of  a  strong  wooden  body,  lined  with  metal, 
with  cells  for  the  reception  of  the  condensing  lenses. 
Openings  at  the  back  shaped  thus  JL  allow  for  the  necessary 
to  and  fro  motion  of  the  lime  jets  and  their  trays. 
Between  these  openings,  on  the  outside  of  the  lantern 
body,  is  fixed  the  dissolving  key  or  tap,  connected  by  india- 
rubber  tubes  with  the  two  jets  (see  fig.  6).    In  front  of  the 


Fig.  6. 

instrument  are  the  stages  for  the  reception  of  the  slides,  and 
the  metal  plates  to  which  are  affixed  the  telescopic  tubes  for 
holding  the  objective  lenses.  These  plates  are  hinged,  and 
their  inclination  upward  or  downward  to  make  the  two 
discs  concentric  on  the  sheet  or  screen  is  governed  by 
milled  headed  screws.  The  objectives  can  by  this  means 
be  made  to  slightly  approach  one  another,  while  the  con- 
densers remain  fixed.    It  is  obvious  that  it  would  be  better 


10 


THE  BOOK  OF  THE  LANTERN. 


if  the  condensing  lens  also  moved  with  the  objective  so 
that  the  optical  axis  of  one  should  agree  with  the 
other.  This  could  easily  be  done  by  making  the  upper 
lantern  move  on  a  central  pivot,  and  clamping  it  with  a 
fixed  screw ;  but  the  more  faulty  and  elaborate  plan  has 
been  adopted  by  manufacturers,  and  will  probably  hold  its 
own  for  a  long  time  yet. 

It  is  certainly  too  much  the  fashion  to  adorn  lanterns 
with  a  mass  of  heavy  brass-work.  Like  any  other  adorn- 
ment, the  brightly-lacquered  brass  looks  well  enough,  but 
represents,  to  my  thinking,  a  waste  both  of  material  and 
of  workmanship,  which  adds  greatly  to  the  cost  of  an 
instrument,  without  adding  one  jot  to  its  efficiency.  In- 
deed, this  brass -work  is  a  positive  disadvantage  when  a 
lantern  has  to  be  carried  from  place  to  place  by  a  busy 
lecturer,  and  constitutes,  not  only  an  inconvenience,  but  a 
tax,  in  the  shape  of  "excess  luggage."  This  superfluous 
metal  must,  I  suppose,  be  looked  upon  as  a  custom  of  the 
trade,  which  it  is  very  difficult  to  break  down.  It  is  the 
same  case  with  the  microscope,  the  delicate  brass-work  of 
which  often  costs  more  than  the  lenses,  expensive  though 
the  latter  are.  In  each  case  the  metal- work  represents  a 
convenience  in  operating  the  instrument,  but  much  of  it 
could  be  dispensed  with,  without  in  any  way  detracting 
from  its  performance.  We  may,  I  think,  gain  a  lesson 
in  the  construction  of  an  ideal  lantern  by  examining 
a  modern  photographic  camera  for  tourists'  use,  where  the 
greatest  rigidity  is  combined  with  extreme  lightness,  and 
metal  is  used  but  sparingly.  Looking  at  such  an 
instrument,  we  find  that  it  must  be  extended  for  f  )cus- 


THE  BOOK  OF  THE  LANTERN. 


11 


sing  purposes,  and  that  its  chief  expanding  part  is  made 
of  folded  leather  (concertina  bellows  fashion).  Now,  why 
should  not  the  same  arrangement  be  adopted  for  the 
optical  lantern  ?  We  here  require  a  similar  extension  of 
the  front  of  the  instrument,  in  order  to  suit  the  foci  of 
the  different  lenses  employed,  and  according  to  the  dis- 
tance and  size  of  the  picture  which  we  wish  to  project  on 
the  screen  before  us.  Surely  some  arrangement  of  the 
kind  could  be  adapted  to  the  lantern.  If  such  a  change 
of  construction  were  brought  about,  and  with  analogous 
alterations  in  other  parts,  the  weight  of  a  double  or  triple 
lantern  would  certainly  be  reduced  to  about  one-third  of 
of  what  it  is  at  present.  It  may,  perhaps,  take  some  time 
for  opticians  to  appreciate  this  view  of  the  case,  and  there 
may  be  good  trade  reasons  for  not  making  a  change  of 
such  a  radical  nature.  I  am  not  behind  the  scenes,  and 
so  cannot  tell.  It  might  certainly  be  urged  with  some 
truth  that  there  is  no  need  to  be  in  a  hurry  to  alter  the 
present  type  of  lantern,  seeing  that  lightness  of  construc- 
tion may  soon  be  brought  about  by  the  substitution  of 
aluminium  for  brass.  The  production  of  the  former 
metal  is  daily  becoming  cheaper,  and  as  its  weight,  bulk 
for  bulk,  is  about  one-third  that  of  brass,  and  as  it  is 
strong,  not  easily  tarnished,  and  in  other  respects  is  suit- 
able for  the  purpose  of  lantern  construction,  we  may  look 
forward  to  its  adoption  in  this  service. 

Where  a  lantern  is  used  for  educational  purposes  it 
requires  certain  additions  which  are  quite  unnecessary  in 
exhibition  instruments.  On  the  other  hand,  several 
ornamental  adjuncts  which  are  desirable  in  the  latter 


12 


THE  BOOK  OF  THE  LANTERN. 


form  of  lantern  may  be  dispensed  with  in  the  instrument 
designed  for  the  lecture  or  school  room.  Indeed,  in  an- 
other chapter  I  point  out  how  a  very  simple  arrangement 


Fig.  7. 

of  lamp  and  lenses  can  be  made  serviceaoie  for  educational 
work.  One  of  the  most  important  additions  to  an  instru- 
ment used  for  teaching  is  what  is  known  as  the 
vertical   attachment.     The  object  of   this  arrangement 


THE  BOOK  OF  THE  LANTERN. 


13 


is  to  show  certain  preparations  and  other  objects  which 
must  be  kept  in  a  horizontal  position  during  exhibition. 
"  Horizontal  Attachment "  would,  therefore,  perhaps  be  a 
more  sensible  name  for  the  apparatus — the  construction  of 
which  can  be  easily  understood  by  reference  to  the  annexed 
cut  (fig.  7).  The  round  opening  in  front,  four  inches  in 
diameter,  is  the  place  where  the  apparatus  fits  on  to  the 
lantern,  the  lenses,  &c,  of  the  latter  having  been  removed 
for  its  accommodation.  So  that  the  light  from  the  lantern  is 
received  by  the  sloping  mirror,  and  is  reflected  upwards 
through  a  condensing  lens,  which  is  placed  horizontally. 
This  lens  forms  a  table  or  stage  upon  which  different  slides 
or  preparations  can  be  laid  for  exhibition.  The  image  is 
formed  by  the  lens  above,  and  by  the  prism  above  that  is 
redirected  and  cast  upon  the  sheet  or  screen.  It  is  obvious 
that  some  loss  of  light  must  result  from  filtering  the  rays 
through  so  many  media,  but  this  cannot  be  helped.  In 
the  chapter  dealing  with  experiments  possible  with  the 
lantern  the  use  of  this  vertical  attachment  will  be  further 
alluded  to,  when  its  value  will  be  better  appreciated. 

Double  lanterns  to  burn  oil  are  usually  placed  side  by 
side,  but  fig.  8  shows  a  convenient  form  of  lantern  which 
has  been  recently  introduced,  and  which  is  so  constructed 
that  one  lantern  can  be  detached  from  its  fellow.  Thus, 
when  the  lime-light  is  used  they  are  adjusted  one  above 
the  other,  and  when  the  oil  lamp  is  employed  they  are 
placed  side  by  side.  Mr.  Tyler  has  still  more  simplified 
the  matter  by  inventiog  a  biunial  lantern  which  burns 
oil,  although  the  position  of  the  two  lamps  is  one  above  the 
other.    This  he  achieves  by  the  use  of  a  bent  chimney, 


14 


THE  BOOK  OF  THE  LANTERN. 


which  proceeds  from  the  lower  lantern  and  carries  away 
the  hot  air,  so  that  it  cannot  influence  the  lamp  above. 


Fig.  8. 


In  the  triple  lantern  (fig.  9)  we  have  three  optical 
systems,  and  of  course  three  lime-lights.  This  is  the 
exhibition  instrument  par  excellence,  and  is  commonly 
used  by  those  exhibitors  who  may  be  described  rather  as 
entertainers  than  lecturers.  The  third  lantern  is  in  reality 
not  often  used.  It  is  kept  in  reserve  for  producing  occa- 
sional effects  while  the  other  two  lanterns  are  at  work. 

In  some  respects  the  optical  lantern  resembles  the  king  of 
musical  instruments,  for  the  effects  which  can  be  produced 
by  it  are  dependent  upon  and  limited  by  the  number  of  its 
parts.  If  an  organ  has  but  one  row  of  keys,  the  instrument 
can  do  little  beyond  furnishing  an  accompaniment.  With 


THE  BOOK  OF  THE  LANTERN. 


15 


two  rows  its  capabilities  are  much  increased,  for  the  organist 
can  use  them  alternately  in  contrast  with  one  another,  or 
can  combine  them.  With  three  claviers,  his  powers  are 
once  more  amplified,  and  he  can  introduce  those  changes 
of  musical  colour  for  which  our  language  provides  no 
descriptive  word.    So  it  is  with  the  lantern.    If  it  have 


Fig.  9. 


but  one  optical  system  the  operator  can  only  use  it  as  a 
means  of  showing  simple  pictures  or  diagrams.  If  it  have 
two  systems  he  can  produce  the  popular  dissolving  views ; 
and  if  it  be  provided  with  a  third  set  of  lenses,  he  can 
mingle  with  the  views  shown  those  "  effects,"  as  they  are 
called,  which  are  so  welcome  to  an  audience  of  young 
folk,  and  very  often  to  children  of  a  larger  growth. 


CHAPTER  II. 


THE  OPTICAL  SYSTEM  OF  THE  LANTERN. 


HE  three  great  essentials  of  a  good  optical  lantern 
are  the  light,  the  condenser,  and  the  objective,  the 
two  latter  forming  the  optical  system  of  the  instru- 
ment. Theoretically,  the  light  to  give  the  best  results  should 
be  a  mere  point  of  radiance,  but  unfortunately  this  is 
at  present  almost  unattainable.  I  say  almost,  because  I 
believe  it  to  be  quite  within  the  bounds  of  possibility  to  con- 
struct an  electric  arc  light  which  shall  f  ulfil  all  the  conditions 
as  to  steadiness,  uniformity  of  action,  and  maintenance  of 
a  fixed  position,  which  are  required  in  lantern  work.  Such 
a  light  has  not  yet  been  found,  but  when  electricity 
becomes  more  general  as  a  source  of  illumination  in  our 
cities  and  towns, — as  it  surely  will, — an  arc  light  or 
regulator  of  the  required  description  will,  I  feel  confident, 
soon  be  forthcoming.  The  invention  of  such  a  con 
trivance,  when  the  means  of  obtaining  the  requisite 
current  to  feed  it  is  so  limited,  would  at  present  have  the 
disadvantage  of  coming  before  its  time.  The  electric 
arc  light  has  been  used  more  than  once  experimentally 
in  the  lantern,  with  the  most  promising  results. 


THE  BOOK  OF  THE  LANTERN. 


17 


The  best  source  of  illumination  .for  the  lantern 
is, — when  we  exclude  electricity  for  the  reasons  just 
indicated,  —  the  lime-light.  It  has  the  good  qualities 
of  intense  whiteness,  steadiness,  ease  of  management, 
portability,  and  although  not  a  point,  its  area  of  radiance 
is  not  much  greater  than  the  space  covered  by  a  pea.  I 
shall  describe  in  detail  the  method  of  its  production  and 
management  later  on. 

Having  then  a  convenient  form  of  intense  light,  we  have 
next  to  consider  the  means  of  using  it  to  the  best  ad- 
vantage. We  must  start  with  the  acknowledgment  that 
in  enlarging  the  image  of  a  picture  we  must  sacrifice  a 
large  amount  of  light.  But  by  using  properly-constructed 
lenses,  we  can  make  this  loss  as  little  as  possible.  As 
already  pointed  out,  the  optical  system  of  a  lantern 
consists  of  two  distinct  parts, — the  eondenser  and  the 
objective  lenses. 

As  many  of  my  readers  may  be  quite  unacquainted  with 


Fig.  10. 

the  matter  under  consideration,  I  will  point  out  why  this 
double  system  is  necessary,  and  describe  the  work  per- 
formed by  each  set  of  lenses.  In  the  annexed  diagram, 
fig.  10,  L  represents  the  lime  cylinder,  with  rays  of  light 
emanating  from  it  and  illuminating  the  picture  P,  which 

c 


18 


THE  BOOK  OF  THE  LANTERN. 


we  require  to  show  in  an  enlarged  form.  0  is  the  objective 
lens  by  which  this  enlargement  is  to  be  brought  about ; 
the  sheet  or  screen  upon  which  the  picture  is  projected 
being  suppose  d  to  be  far  away  to  the  right.  With  such  an 
arrangement  of  parts  what  should  we  see  on  that  screen  ? 
In  the  first  place  we  should  have  but  a  very  feeble  light, 
for  as  will  be  seen  by  reference  to  the  diagram,  most  of 
the  luminous  rays  are  wasted  altogether,  only  the  cen- 
tral ones  proceeding  through  the  lens  O.  It  will  be 
seen  also  that  these  rays  go  through  the  central  portion 
of  the  picture  only,  and  that  therefore  only  this  part 
can  be  projected  on  to  the  distant  screen.  So  that  as  a 
result  of  our  first  efforts  at  lantern  projection,  we  get  an 
indistinct  and  badly-lighted  portion  of  a  picture  presented 
to  us.  How  can  we  remedy  this  state  of  things  ?  Ob- 
viously, the  thing  to  be  done  is  to  cause  more  of  the  rays 
from  our  light  source  to  be  utilised,  and  tnis  can  be  brought 
about  by  placing  between  that  light  and  the  picture  a  lens 
which  shall  condense  the  light  upon  that  picture,  and  which 
is  therefore  known  as  the  condenser. 

In  fig.  11  we  see  a  repetition  of  the  diagram,  fig.  10,  with 


Fig.  11. 

the  addition  of  a  condenser,  shown  m  this  case,  for  the 
sake  of  simplicity,  as  a  single  lens.    Referring  once  more 


THE  BOOK  OF  THE  LANTERN. 


1!) 


to  this  imaginary  picture  upon  our  screen,  we  now  see  that 
it  is  complete.  It  is  no  longer  the  central  fragment  of  a 
design,  but  covers  the  sheet,  and  is  equally  illuminated. 
We  can  at  once  see  the  reason  for  this  welcome  change  by 
looking  once  more  at  our  revised  diagram,  fig.  11.  The 
rays  of  light  instead  of  being  wasted  in  illuminating  the 
inside  of  the  lantern  box,  are  refracted  by  the  lens  which 
we  have  introduced,  and  are  bent  towards  the  objective. 

In  my  diagrams,  for  the  sake  of  simplicity,  I  have 
represented  each  lens  as  consisting  of  a  single  piece  of 
glass  of  plano-convex  form.  Such  lenses  are  found  in  toy 
lanterns  of  the  cheapest  kind,  but  are,  as  might  be  ex- 
pected, extremely  faulty  in  performance.  In  the  enlarged 
picture,  they  give,  owing  to  their  total  want  of  correction, 
badly-defined  margins,  curved  lines,  and  fringes  of  colour. 

Having  now  seen  the  purpose  fulfilled  by  the  condensir  g 
lens  of  the  optical  lantern,  let  us  further  consider  its  best 
form,  and  let  me  at  once  correct  an  error  into  which  a 
purchaser  is  likely  to  fall.  I  have  sometimes  heard  the 
possessor  of  a  lantern  speak  somewhat  boastingly  of  his 
instrument  as  one  with  5,  or  perhaps  6-inch  condensers, 
the  more  ordinary  size  being  4  inches,  and  often  only 
3|  inches.  For  lantern  projection,  any  size  over  4  inches 
is  a  positive  disadvantage,  and  instead  of  representing  a 
gain,  means  really  a  great  loss  of  light.  The  reason  for 
this  is  readily  seen.  What  may  be  called  the  standard  size 
for  a  lantern  picture  is  3  inches  in  diameter  (the  entire 
slide  with  its  margin  measuring  3^  inches).  If  the  picture 
be  framed  in  a  circular  3-inch  mount,  a  3|-inch  condenser 
will  amply  illuminate  it.    If,  however,  the  orifice  of  the 


20 


THE  BOOK  OF  THE  LANTERN. 


mount  be  square  or  cushion-shaped,  such  a  small  condenser 
would  infallibly  cut  off  the  corners  of  the  projected  image, 
and  for  such  pictures,  therefore,  a  4-inch  condenser  is 
necessary.  But  the  smaller  condenser  transmits  more 
light,  for  the  reason  that  being  of  shorter  focus,  the  lime 
cylinder  is  brought  nearer  to  it.  Some  well-known 
exhibitors,  seeing  the  great  importance  of  getting  all  the 
light  upon  the  screen  that  they  possibly  can,  use  nothing 
but  3 J- inch  condensers,  but  this  obliges  them  to  confine 
themp elves  to  round  pictures.  On  the  whole,  I  prefer 
myself  the  4 -inch  condenser,  for  although  I  lose  some 
light,  I  can  make  use  of  any  shaped  pictures  or  diagrams 
which  may  be  required.  (If  the  lantern  be  used  for 
photographic  enlarging  purposes,  then  a  large-sized  con- 
denser is  the  great  thing  needful,  at  least,  we  must  have 
one  of  a  size  large  enough  to  cover  the  negative  which 
has  to  be  enlarged  ;  a  quarter-plate  size  necessitating  a 
5 -inch  condenser  and  so  on.  But  in  that  case  brilliancy 
of  image  is  quite  a  secondary  matter,  and  is  compensated 
for  by  extension  of  time  occupied  in  the  operation.)  It 
must  also  be  borne  in  mind  that,  quite  apart  from  the 
question  of  focal  length  of  the  condensing  lens,  there  is  a 
limit  to  the  near  approach  of  the  incandescent  lime 
cylinder  towards  it,  for  the  intense  light  is  naturally  ac- 
companied by  a  fervent  heat,  which  will  surely  crack 
a  lens  if  it  be  too  near  to  it.  In  the  chapter  on  the 
working  of  the  lime -light,  precautions  against  this  accident 
are  fully  dealt  with. 

There  are  two  forms  of  condensers,  either  of  which 
may  be   commonly  found  in  commercial  lanterns.  One 


THE  BOOK  OF  THE  LANTERN. 


21 


consists  of  a  pair  of  plano-convex  glasses  mounted  in  one 
cell,  with  their  curved  surfaces  all  but  touching  one  another. 
This  form  was,  I  believe,  first  introduced  with  the 
American  sciopticon.  It  is  shown  at  fig.  12.  The  other 
form  of  condenser  is  that  devised  (but  not  for  lantern  use) 
by  Sir  John  Herschell,  and  which  consists  of  a  double 


Fig.  12.  Fig.  13. 

convex  lens,  associated  with  a  meniscus,  the  concave  side 
of  the  latter  being  next  the  radiant  point,  as  shown  in 
fig.  13.  In  a  good  condenser  we  want  not  only  quantity 
of  light,  but  also  good  quality,  and  these  properties  can 
only  be  secured  by  careful  attention  to  certain  points  of 
construction.  Quantity  of  light  is  governed  by  size  and 
focal  length,  as  already  pointed  out,  and  it  may  be  as  well 
to  indicate  here  the  manner  in  which  lanterns  furnished 
with  condensers  of  larger  size  than  I  have  recommended 
may  be  made  to  transmit  a  greater  amount  of  light  by  the 
inter  j  osition  of  another  lens.  There  were  at  the  old  Poly- 
technic Institution  some  antique  lanterns  with  10-in.  con- 
densers, this  large  size  being  necessary  to  cover  the  8 -in. 
hand-painted  transparencies  which  were  in  use  before 
photography  worked  a  revolution  in  such  things.  Such  a 
large  condenser,  of  course,  meant  a  great  loss  of  light,  as 


22 


THE  BOOK  OF  THE  LANTERN. 


already  pointed  out.  So  the  suggestion  was  made  that  a 
small  lens  should  be  interposed  between  the  light  and  the 
condenser.  This  was  done  with  a  wonderful  gain  in  the 
performance  of  the  old  lanterns.    Fig.  14  will  show  how 


Fig.  14. 


the  additional  lens  brought  this  improvement  about.  Many- 
other  forms  of  condensing  lenses  have  from  time  to  time 
been  suggested  and  experimented  with,  some  of  these  em- 
ploying three  or  more  combinations.  But  these  various 
patterns,  although  one  or  two  of  them  seem  very  promising 
in  form,  have  not  been  taken  in  hand  by  makers  generally, 
—  possibly  on  the  score  of  expense,  and  probably  owing  as 
much  to  that  hesitation  and  laziness  common  to  human 
nature,  which  keeps  us  all  to  a  well-beaten  track. 

But  a  few  years  ago  the  question  of  lantern  lenses  was 
revived  by  a  paper  read  by  the  late  Mr.  J.  H.  Dallmeyer 
before  the  Photographic  Society  of  Great  Britain.  The 
reader  of  this  excellent  contribution  to  the  subject,  explained 
in  the  first  instance  that  a  well-known  worker  with  the 
lantern  had  called  his  attention  to  the  great  want  of  more 


THE  BOOK  OF  THE  LANTERN 


23 


perfect  lenses  for  use  with  the  instrument.  Mr.  Da  limey  er 
thereupon  determined  to  tackle  the  subject,  and  produced 
new  forms  of  condensers  and  objectives,  a  description  of 
which  he  placed  before  the  Photographic  Society.  I  can- 
not do  better  than  quote  the  description  of  the  new  con- 
denser from  this  paper,  and  at  the  same  time  reproduce 
one  of  the  drawings  shown  in  illustration  of  the  remarks 
made  (see  fig.  15) : — 


R 

A  |  J 

B 

r  " — 

Fig.  15. 


The  condenser  is  of  4-in..  effective  diameter,  and  2f- 
in.  equivalent  focal  length.  Assuming  the  light  to  be  at 
a  safe  distance  of  2f  in.  from  the  flat  surface  of  the  first 
lens,  this  condenser  collects  an  angular  pencil  of  about 
66°,  i.e.,  about  20  per  cent,  more  light  than  the  shortest 
focus  symmetrical.  It  consists  of  two  unsymmetrical 
lenses,  A  and  B.  A  is  a  plano-convex  of  flint  3|-in. 
diameter,  and  B  is  a  double  convex  of  crown  glass  of  4-in. 
diameter.  The  lenses  are  mounted  at  a  certain  distance 
apart,  with  their  deep  sides  facing  each  other.  Approxi- 
mate correction  of  chromatic  aberration  for  centrical  pencils 
is  obtained  by  a  proper  apportioning  of  their  focal  lengths, 
and  the  distance  at  which  they  are  placed.    Thus  :  ray 


24 


THE  BOOK  OF  TILE  LANTERN. 


L  R,  after  refraction  by  lens  A,  diverges  into  a  prismatic 
beam  ;  this  falls  upon  different  parts  of  lens  B,  which, 
while  acting  upon  the  two  extremes, — the  red  and  the 
violet, — in  contrary  directions  to  A,  canses  them  to  emerge 
parallel,  the  condition  of  achromatism,  when  they  converge 
to  the  conjugate  focus  f,  about  9  in.  removed  from  B.  The 
spherical  aberration  is  reduced  to  a  minimum  by  the  forms 
of  the  lenses  employed,  i.e.,  ray  Lr,  refracted  by  the  central 
portions  of  the  lenses,  meets  the  axis  at  the  same  point  f9 
as  the  marginal  rays,  or  nearly  so.  I  have  decided  upon  a 
4-in.  (effective)  diameter  condenser,  since  it  fully  illumi- 
nates the  corners  of  a  2|-in.  square  slide.  Of  course,  a 
circular  slide  of  3  in.  only  requires  a  3J-in.  diameter  con- 
denser, of  proportionately  shorter  focal  length.  I  need 
hardly  say  that  the  glass  composing  this  condenser  has 
been  selected  with  esp:cial  care.  It  is  perfectly  limpid,  or 
colourless,  and  will  remain  so  ;  it  is  free  from  strice  and  air 
bubbles,  and  has  a  perfect  polish.  In  fact,  it  is  Chance's 
best  glass  ;  the  only  drawback  being  its  cost." 

Mr.  Dallmeyer  goes  on  to  remark  that  the  defects  in  the 
glass  of  a  lantern  condenser,  are  of  far  more  importance  than 
similar  defects  in  the  objective,  so  far  as  purity  and  quality 
of  the  illuminated  disc  are  concerned.  He  refers  to  such 
defects  as  scratches,  air-bubbles,  and  the  like.  In  the  case 
of  an  air-bubble  in  the  objective  lens,  it  is  really  of  no 
moment  whatever.  I  have  known  of  a  photographic  lens, 
otherwise  of  splendid  quality,  being  rejected  because  of 
a  tiny  air-bubble  near  its  margin,  the  purchaser  being  quite 
content  to  exchange  it  for  a  far  inferior  lens  without  such 
an  insignificant  blemish.    Such  a  bubble  would  have  no 


THE  BOOK  OF  THE  LANTERN. 


25 


effect  whatever  upon  the  performance  of  the  lens,  whether 
used  with  a  camera,  or  as  a  lantern  objective,  supposing  it 
to  be  suitable  to  lantern  work  in  other  respects.  But 
transfer  the  bubble  from  the  objective  to  the  condenser,  and 
it  at  once  constitutes  a  real  eyesore,  which  will  be  terribly 
magnified  on  the  screen.  For  this  reason  lantern  owners 
should  take  the  greatest  care  to  prevent  their  condensers 
becoming  scratched,  for  a  mark  hardly  visible  on  the  glass 
will  become  fatally  apparent  on  the  screen. 

It  will  be  seen,  from  what  has  gone  before,  that  the  duty 
of  the  condensing  lens  is  to  take  up  and  utilise  as  large  a 
bundle  of  light  rays  as  is  practicable,  and  with  those  rays  to 
brightly  illuminate  the  whole  of  the  picture  or  slide  placed 
against  it.  The  other  part  of  the  optical  system  of  the 
lantern  is  the  objective  lens,  which  is  destined  to 
form  a  magnified  image  of  that  picture  or  slide.  To  this 
important  part  of  the  apparatus  I  must  now  turn  the 
reader's  attention. 

As  the  duty  of  the  condenser  is  to  give  the  greatest 
amount  of  illumination  to  the  lantern  picture  or  slide,  so 
the  province  of  the  objective  lens  is  to  form  as  perfect  as 
possible  a  magnified  image  of  that  picture  upon  the  screen 
or  sheet  placed  for  its  reception.  Toy  lanterns  are  fre- 
quently fitted  with  a  doub'e  convex,  the  worst  form  of  all, 
or  with  a  plain  convex  lens,  which  is  little  better.  With 
regard  to  lanterns  of  more  pretension,  we  find  that  different 
makers  adopt  different  forms  and  combinations  for  their 
objectives.  Some  use  a  couple  of  plano-convex  achromatic 
lenses,  in  conjunction  with  a  stop  or  diaphragm,  the  flat 
sides    of   the    lenses    being    next    the    light  ;    a  very 


2b 


THE  BOOK  OF  THE  LANTERN. 


good  form  indeed,  provided  that  the  lenses  are  of  sufficient 
diameter  bo  take  in  the  entire  cone  of  rays  from  the  con- 
denser. This  has  always  been  a  stumbling-block  in 
adjusting  lenses  of  short  focus  to  the  lantern,  for  it  stands 
to  reason  that  the  shorter  the  focus  the  nearer  must  the 
lens  be  to  the  condenser,  and  if  the  diameter  of  the 
lens  be  small  a  large  proportion  of  the  rays  will  not  get 
through  at  all. 

And  this  question  of  focus  of  the  objective  is  one  that 
must  be  carefully  considered  by  all  who  use  a  lantern. 
Many  are  of  the  opinion  that  the  focal  length  of  the  objec- 
tive used  should  be  so  short  that  the  distance  of  the 
lantern  from  the  screen  should  be  about  the  same  as  the 
diameter  of  that  screen.  In  private  rooms  of  small  size 
this  may  be  necessary,  if  not  advantageous,  but  in  larger 
rooms  or  lecture-halls  a  lens  which  will  triple  or  quadruple 
that  distance  is  desirable.  Much  experience  of  lecture- 
hall  work  has  led  me  to  the  conclusion  that  a  lens  of  8-inch 
focus  is  more  useful  as  a  lantern  objective  than  any  other, 
and  it  is  as  well  to  have  one  of  10  inches  in  reserve  in 
case  the  length  of  the  hall  should  require  it.  Let  me  give 
my  reasons  for  this  choice.  I  find  that  the  size  of  sheet 
most  commonly  required  in  rooms  used  for  lecture  pur- 
poses is  15  feet.  Some  rooms  will  take  an  18-foot  sheet,  and 
very  few  take  a  larger  one  than  that.  But  the  15 -foot  screen 
is  the  one  most  in  request.  .Now  let  us  suppose  the  operator 
has  fitted  to  his  lantern  an  objective  of  say  4 \ -inch  focus. 
To  cover  his  15-foot  screen  he  must  plant  his  lantern  less 
than  20  feet  from  it,  a  distance  which  will  land  him  in 
the   middle   of   the   front   seats.      His  apparatus  will 


THE  BOOK  OF  THE  LANTERN. 


27 


in  such  a  case  terribly  impede  the  view  of  all  those 
behind  the  lantern,  besides  causing  much  disarrange- 
ment of  chairs.  But  let  him  use  an  8-inch  objective, 
and  his  lantern  can  he  carried  to  a  distance  of 
35  feet  from  the  screen.  This  will  probably  place  the 
lantern  quite  at  the  back  of  the  hall.  Another  point  in 
favour  of  the  latter  position  is,  that  if  his  two  lenses  are  of 
the  same  diameter,  as  most  probably  they  will  be,  the  long, 
focus  lens  will  admit  more  light,  as  already  explain e  I ; 
while  it  will  certainly  give  better  definition  and  less  dis- 
tortion than  the  shorter  focus  lens.  One  more  circum- 
stance in  favour  of  the  longer  focus  lens  is,  that  the  lantern 
is  kept  more  horizontal.  When  the  instrument  is  close  to 
the  screen,  unless  the  floor  of  the  auditorium  be  inclined, 
as  in  a  proper  lecture -theatre,  the  lantern  must  be  very 
much  tipped  up  at  its  fore-end,  so  that  the  disc  on  the  sheet 
shall  be  high  enough.  This  raising  of  the  lantern,  of 
course,  leads  to  distortion,  unless  the  screen  be  inclined 
towards  the  lens  so  as  to  compromise  the  matter.  With  a 
long-focus  lens  the  distortion  from  this  cause  is  greatly 
reduced,  and  very  often  it  is  so  slight  that  there  is  no  need 
to  incline  the  sheet.  I  hold  the  opinion  that  a  good  single 
achromatic  lens  of  long  focus  is  by  no  means  to  be  despised 
for  lantern  work,  although  a  half -plate  lens  of  the  portrait 
type  is  to  be  preferred.  Such  a  lens  can  only  be  used  for 
the  long-distance  work.  If  it  is  absolutely  necessary  that 
the  lantern  be  as  near  the  sheet  as  possible,  then  it  is  com- 
monly the  fashion  to  use  a  French  quarter-plate  photographic 
lens, — I  presume  on  account  of  its  cheapness.  For  it  is 
most  difficult  to  select  a  lens  of  this  description  which  will 


28 


THE  BOOK  OF  THE  LANTERN. 


give  a  flat  field,  and  the  ordinary  diameter  of  the  back  lens 
of  such  a  combination  will  not  admit  the  whole  of  the 
rays  from  the  condenser :  hence  we  are  robbed  of  light, 
and  very  often  of  the  corners  of  square  pictures  into  the 
bargain. 

Of  late  years  makers  have  seen  these  disadvantages,  and 
have  produced  lantern  objectives  which,  while  they  are 
similar  in  construction  to  portrait  objectives,  are  made  with 
much  larger  apertures  at  the  back.  Taking  Mr.  Dallmeyer's 
lantern  objective  as  the  prototype  of  these,  we  find  that  it 
consists,  like  the  portrait  lens,  of  two  combinations.  The 
back  one,  next  the  light,  is  a  convexo-concave  of  flint,  and 
another  of  crown  glass,  separated  by  a  short  interval,  the 
two  glasses  being  dissimilar  in  their  curvature.  The 
external  form  of  this  combination  is  a  meniscus,  its  convex 
surface  being  next  the  condenser.  The  front  combination, 
of  smaller  diameter,  also  has  the  external  meniscus  form, 
but  consists,  like  its  fellow,  of  two  glasses. 

It  must  be  noted  that  objectives  made  for  lantern  work 
are  not  suitable  for  photography,  for  the  visual  and  chemical 
rays  are  not  coincident.  I  mention  this  for  the  sake  of 
those  who  wish  to  use  the  lantern  as  an  aid  to  their  photo- 
graphic pursuits,  in  enlarging  and  so  on.  It  may,  therefore, 
be  in  some  cases  desirable  for  the  purchaser  to  obtain  a 
half -plate  portrait  lens  for  his  lantern.  It  will  do  excellent 
work,  with  the  limitation  already  referred  to,  while  at  the 
same  time  it  can  be  used  either  for  portraiture  or  for 
enlarging.    For  both  these  uses  it  is  well  adapted. 

The  rule  for  calculating  the  distance  of  the  lantern  from 
the  screen  in  order  to  obtain  an  image  of  a  given  size  will 


THE  BOOK  OF  THE  LANTERN. 


29 


be  found  on  pnge  95,  bat  in  practice  I  find  it  a  convenient 
thing  to  nse  a  tape  measure.  Upon  the  circular  case  of 
this  measure  I  have  certain  figures  to  the  effect  that  such 
and  such  a  lens  requires  a  distance  of  so  many  feet  to  give 
a  15  or  18  foot  disc.  The  place  of  the  sheet  having  been 
decided  upon,  it  is  then  easy  enough  to  pay  out  the 
required  amount  of  tape,  and  to  fix  the  position  of  the 
lantern. 


CHAPTER  III. 


OXYGEN    GAS  MAKING. 

HE  first  requisite  for  the  lime -light  is  an  adequate 
quantity  of  oxygen  gas,  and  this  chapter  will, 
'  therefore,  be  devoted  to  the  details  of  its  manu- 
facture, or  rather  its  separation  from  those  substances  with 
which,  in  nature,  it  is  associated.  For,  although  the  most 
abundant  of  all  the  elements,  oxygen  does  not  occur  in 
the  uncombined  state,  and,  therefore,  the  chemist  has  to 
be  at  the  pains  of  separating  it  from  its  various  yoke- 
fellows. There  are  several  methods  of  obtaining  this  gas ; 
the  greater  number  of  which,  being  only  of  experimental 
interest,  may  be  passed  over. 

The  gas  was  originally  discovered  by  Priestley  in  1774, 
and  at  about  the  same  time,  independently,  by  the  Swedish 
chemist,  Scheele.  Priestley  obtained  it  by  heating  mer- 
curic oxide  in  a  flask,  which  substance,  under  such  treat- 
ment, breaks  up  into  mercury  vapour  and  oxygen  gas. 
Such  a  method  is  clearly  out  of  the  question,  when  several 
feet  of  gas  are  required  for  the  lime-light. 

Another  method,  which  is  applicable  when  large  quan- 
tities of  oxygen  are  wanted,  and  which  has   long  been 


THE  BOOK  OF  THE  LANTERN. 


31 


adopted  on  a  commercial  scale,  depends  npon  the  action  of 
cobalt  on  bleaching  powder  (Calcic  hypochlorite).  The 
lime  mnst  be  in  the  form  of  a  concentrated  solntion,  and 
this  is  best  bronght  abont  by  mixing,  say,  one  ponnd  of 
bleaching  powder,  which  is  commonly  called  chloride  of 
lime,  with  a  qnart  of  water.  Stir  this  mixture  and  allow 
it  to  remain  for  an  hour.  Now  decant  the  clear  liquid, 
and  pour  it  upon  a  fresh  pound  of  lime — stir  as  before, 
and  strain  the  product  through  a  calico  or  flannel  bag. 
Place  the  liquid  in  a  large  bottle,  to  the  cork  of  which 
a  tube  is  fitted.  Now  drop  into  the  liquid,  taking  the 
cork  out  for  the  time  being,  a  small  quantity  (say  2  ounces) 
of  a  strong  solution  of  cobaltic  peroxide,  when  oxygen  gas 
will  be  quickly  evolved,  and  will  come  off  through  the 
replaced  tube.  The  evolution  of  gas  is  increased  by 
warmth.  The  same  cobalt  can  be  used  again  and  again,  as 
it  does  not  undergo  any  permanent  change.  It  seems  to 
act  merely  as  a  conveyer  of  oxygen,  taking  it  from  the 
lime,  passing  it  to  a  higher  state  of  oxidation,  and  then 
giving  it  up  again  ;  any  solution  of  cobalt  will  answer  the 
purpose.  When  the  gas  ceases  to  come,  the  residue  in  the 
bottle  should  be  diluted  with  water,  and,  after  having  been 
allowed  to  rest  for  some  time,  the  cobalt  will  settle  at  the 
bottom  of  the  vessel.  This  can  then  be  washed,  kept  in  a 
moist  state,  and  used  over  again  as  often  as  required. 

But  the  more  general  method  of  preparing  the  gas  is  by 
means  of  the  decomposition  of  potassic  chlorate,  and 
that  method  I  shall  now,  therefore,  describe  in  detail. 

The  lime-light  has,  in  certain  quarters,  earned  the  cha- 
racter of  being  dangerous,  not  so  much  from  accidents 


32 


THE  BOOK  OF  THE  LANTERN. 


which  have  occurred  during  its  use,  but  more  from  certain 
catastrophes  which  have  taken  place  during  the  preli- 
minary operation  of  making  oxygen  gas.  There  should  be 
no  danger  whatever  about  this  operation  if  only  ordinary 
precautions  are  taken.  But  some  people  seem  to  be  unable 
to  do  things  except  in  a  haphazard  manner,  and  they 
sooner  or  later  pay  the  penalty  for  their  carelessness. 

The  most  important  point  to  begin  with  is  to  have 
proper  apparatus ;  and  by  this  I  do  not  mean  the  most  ex- 
pensive, for  this  is  just  as  often  as  not  faulty  in  point  of 


I 


Fig.  16. 

construction.  The  articles  required  are :  A  retort  in 
which  to  generate  the  gas ;  a  stove  for  heating  that  retort 
(preferably  a  gas  ring-burner)  ;  a  wash  bottle,  or  purifier ; 


THE  BOOK  OF  THE  LANTERN. 


33 


several  feet  of  good  rubber  tubing ;  and  a  bag  to  hold  the 
gas  when  made.  The  retort  which  I  prefer  is  Oakley's 
pattern,  and  is  made  of  wrought  iron,  brazed  and  rivetted 
together,  and  of  the  form  shown  in  the  accompanying 
sketch,  fig.  16.  It  will  be  noticed  that  it  is  of  conical  form, 
and  that  its  lower  part,  where  it  rests  on  the  stove,  is  con- 
vex in  shape.  It  terminates  at  the  mouth  with  a  brass 
screw,  and  in  this  screw  fits  a  branch,  or  pipe,  which  con- 
veys the  gas  away  as  fast  as  it  is  generated.  An  important 
point  in  this  branch  is  the  arched  bend,  immediately  over 
the  retort,  which  obviates  undue  friction,  and  also  prevents 
any  solid  particles  given  off  from  the  retort  clogging  or 
stopping  up  the  tube.  With  that  provision  one  element 
of  danger  is  avoided.  Another  point  of  importance  is  the 
•little  upright  tube,  or  nozzle,  immediately  above  that  same 
bend.  This  is  merely  a  short  piece  of  tubing  fixed  on  to 
the  branch,  and  in  which  a  cork  can  be  fitted.  This  acts 
as  a  simple  safety-valve.  Should  the  pressure  of  gas 
become  too  great,  the  cork  will  fly  out  and  no  damage  can 
possibly  occur,  except  the  loss  of  a  very  small  quantity 
of  gas. 

There  are  various  other  forms  of  retort  which  are  used 
and  recommended  by  different  operators.  A  cast-iron  one 
is,  of  course,  more .  lasting ;  but  in  case  of  accidental  explo- 
sion, its  particles  would  be  as  deadly  as  those  of  a  bomb- 
shell. But  such  an  explosion  should  never  occur,  if 
ordinary  care  be  taken.  With  some  persons,  familiarity 
with  the  most  dangerous  agents  so  rapidly  breeds  con- 
tempt, that  they  get  careless  in  a  very  short  time.  We 
may  suppose  that  this  happened  in  the  case  of  an  optician, 


34 


THE  BOOK  OF  THE  LANTERN. 


who  some  years  ago  was  killed  by  such  an  explosion  of  an 
oxygen  retort. 

Many  old-fashioned  operators  nse  an  iron  mercury 
bottle  as  a  retort,  and  this,  I  believe,  was  the  invariable 
custom  when  oxygen  was  procured  from  manganese  per- 
oxide alone.  The*  heat  required  was  so  great  that  a  thick 
and  lasting  receptacle  was  necessary.  But  now-a-days, 
when  chlorate  is  used  so  universally,  the  gas  comes  off  at  a 
much-reduced  temperature,  and  a  thin  retort  will  last,  with 
care,  for  about  fifty  charges.  My  lantern  assistant  prefers 
to  use  a  kitchen  digester,  which  he  has  had  fitted  with 
a  pipe  and  safety  cap,  and  which  he  regards  as  a  triumph 
of  art,  which  will  not  only  last  his  own  life-time,  but  will 
be  handed  down  to  his  descendants  as  an  heir-loom.  One 
more  word  on  the  subject  of  retorts.  Do  not  buy  a  copper 
one ;  it  is  very  expensive,  and  quickly  wears  out,  and  has 
no  advantages  whatever.  In  case  a  retort  should  be 
wanted  in  a  hurry,  and  cannot  be  obtained,  a  common 
cast  iron  kettle  is  a  capital  substitute  for  one.  Put  the 
chlorate  mixture  in  the  kettle,  and  fasten  on  the  lid  with 
a  luting  of  white  lead  or  clay  ;  cut  a  piece  of  firewood 
to  the  correct  size,  to  fit  tightly  between  the  lid  and 
the  inside  of  the  handle  of  the  kettle,  so  that  no  pressure 
will  force  it  open.  Use  the  spout  as  a  delivery  tube  of  the 
gas. 

The  retort  is  charged  with  a  mixture  of  chlorate  of  potash 
and  oxide  of  manganese,  and  the  most  usual  proportions 
are  four  parts  by  weight  of  the  potash  to  one  part  of  the 
manganese. 

This  is  the  mixture  as  given  in  the  various  chemical  text- 


THE  BOOK  OF  THE  LANTERN. 


35 


books  ;  but,  as  a  matter  of  fact,  the  exact  proportion  is  not 
of  very  great  consequence.  Indeed,  it  would  seem  that  if 
the  crystals  of  potash  have  mixed  with  them  just  sufficient 
of  the  black  manganese  to  dirty  them  well,  the  mixture 
will  be  effective. 

Oxygen  gas  can  be  generated  from  the  chlorate  alone, 
but  the  action  is  so  uncertain  that  the  salt  is  always  mixed 
with  manganese,  oxide  of  iron,  or  sand.  What  action  the 
manganese  has  upon  the  mixture  is  not  known,  for  it  is 
a  curious  fact  that,  after  the  operation  is  over,  it  remains 
unchanged,  so  that  it  is  possible,  if  one  cared  to  take  the 
trouble,  to  preserve  it  and  use  it  over  and  over  again. 
Where  manganese  is  difficult  to  obtain,  this  method  may 
be  adopted,  but  in  most  towns  it  can  be  procured  at  such 
a  cheap  rate  that  such  a  course  would  simply  represent  a 
waste  of  time  and  trouble. 

The  greatest  care  should  be  exercised  in  procuring  both 
components  of  the  oxygen  mixture  in  an  unadulterated 
state.  The  ordinary  commercial  chlorate  is  quite  good 
enough  for  the  purpose,  and  although  it  has  the  disadvan- 
tage of  being  contaminated  with  a  certain  amount  of  free 
chlorine  which  is  given  off:  in  gas-making,  it  would  be 
a  useless  expense  to  employ  the  pure  salt,  as  used  for 
medicinal  purposes.  Moreover,  the  chlorine  can  be  got  rid 
of,  as  we  shall  presently  see,  by  simple  means.  But  in 
most  samples  of  commercial  chlorate  there  are  to  be  found 
certain  foreign  bodies,  such  as  bits  of  straw,  bits  of  wood 
(from  the  casks  in  which  the  chlorate  is  originally  sold), 
and  other  specimens  of  matter  in  the  wrong  place,  which 
would  be  prejudicial  to  the  operation  of  gas-making,  and, 

J>2 


36 


THE  BOOK  OP  THE  LANTERN. 


indeed,  dangerous  ;  for  carbonaceous  material,  when  mixed 
with,  the  chlorate,  constitutes  a  very  powerful  explosive. 
(As  an  instance  of  this,  I  may  mention  that  in  the  greatest 
explosion  of  modern  times,  when  thousands  of  tons  of 
explosive  material  were  fired  for  the  purpose  of  destroying 
the  "  Hell-Gate  Rock "  at  the  entrance  of  New  York 
Harbour,  a  large  proportion  of  the  chemicals  employed 
consisted  of  chlorate  of  potash  combined  with  coal-dust.) 
Before  mixing  the  ingredients  together,  therefore,  the 
crystals  of  potash  should  be  carefully  picked  over  by  hand, 
and  any  unconsidered  trifles  which  have  no  business  to  be 
present  should  be  carefully  extracted  from  it.  A  little  care 
is  also  necessary  with  regard  to  the  manganese.  Accidents 
have  happened  from  lampblack,  bone-dust,  and  other  similar 
compounds,  having  been  substituted  (let  us  hope  by  acci- 
dent) for  the  manganese  that  was  intended  to  be  used.  In 
buying  fresh  samples,  therefore,  of  manganese,  it  should 
be  carefully  tested,  and  the  best  way  of  doing  this  is  to  mix 
up  a  small  quantity  of  the  potash  and  the  manganese  in 
the  proportions  above  given,  and  to  put  them  in  a  test 
tube,  which  should  be  held  over  the  flame  of  a  spirit  lamp. 
If  the  mixture  simply  sparkles  while  oxygen  gas  is  given 
off  at  the  mouth  of  the  tube  (as  may  be  tested  by  the  spark 
on  a  blown-out  match),  the  mixture  is  safe  ;  but  if  any- 
thing in  the  least  resembling  an  explosion  should  take  place, 
the  manganese  is  wrong,  and  must  be  rejected.  Bat  the 
operator  is  not  liable  to  fall  into  the  error  of  mistaking 
lampblack  or  bone-dust  for  manganese,  because  they  are, 
bulk  for  bulk,  so  very  much  lighter  than  that  heavy 
earth. 


THE  BOOK  OF  THE  LANTERN. 


37 


The  mixture  having  been  made,  enough  of  it  must  be 
placed  in  the  retort  to  give  the  amount  of  gas  which  we 
require.  It  will  be  found  that  if  we  allow  one  pound  of 
chlorate  to  every  4  feet  of  gas,  it  will  be  about  right. 
Roughly  speaking,  a  bag  of  8  feet  capacity, — a  very  useful 
size, — will  take  2^  lb.  of  the  mixture,  and  it  is  better  to 
waste  a  little  chlorate  than  to  have  a  bag  which  is  not 
quite  full.  Having  charged  the  retort  with  the  mixture, 
we  can  screw  on  the  delivery  branch,  taking  care  to  insert 
a  washer  of  leather  or  asbestos  cloth,  to  prevent  any  escape 
of  gas  between  branch  and  retort. 

In  using  a  new  retort,  it  is  always  well  to  blow 
into  it  while  the  branch  is  fixed  in  position,  so  as  to  be 
quite  sure  that  there  is  no  leak  in  the  joints  which  has 
escaped  the  maker's  attention.  Should  a 
leak  be  discovered,  a  little  white  lead  will 
remedy  it  for  the  time  being.  The  retort 
may  now  be  placed  on  the  gas-stove,  while 
its  branch  rests  upon  a  chair  or  other 
support.  A  tube  at  least  4  feet  long,  and 
of  a  diameter  agreeing  with  that  of  the 
branch  of  the  retort,  should  be  drawn 
over  that  branch  for  about  2  inches.  The 
other  end  of  this  tube  is  to  be  connected 
with  the  wash-bottle. 

The   kind  of   wash  bottle   which  I 
use,  and  which  I  can  recommend  very 
highly,  is  also  made  by  Oakley  &  Co.         Fig.  17. 
of   Bermondsey    (fig.    17).      It    is    of   half    a  gallon 
capacity,  and  is  in  reality  a  glass  "  Winchester  quart " 


38 


THE  BOOK  OF  THE  LANTERN. 


bottle  with  a  wide  neck,  such  as  can  be  obtained  anywhere. 
Upon  this  neck  fits  a  disc  of  lead,  perforated  with  two  holes, 
in  which  are  soldered  as  fixtures  two  pewter  tubes  which 
bend  away  from  one  another  at  their  tops. 

One  tube,  A,  reaches  nearly  to  the  bottom  of  the  bottle, 
and  it  will  be  seen  that  for  several  inches  along  its  lower 
part  it  is  perforated  with  holes.  It  is  this  tube  which  is 
connected  by  a  rubber  pipe  to  the .  retort.  The  dotted 
line  shows  the  height  to  which  the  bottle  must  be  filled 
with  water.  The  short  tube,  B,  is  the  delivery  tube  of 
the  bottle,  and  is  connected  with  the  gas  bag.  As  a  gas- 
tight  connexion  between  the  pewter  disc  and  the  bottle, 


Fig.  18. 


there  is  a  thick  rubber  collar,  which  is  tied  on  the  bottle 
by  means  of  a  piece  of  strong  twine.  The  larger  sectional 
diagram  of  the  bottle  neck  (see  fig.  18)  will  assist  the 
reader  in  noting  the  arrangements  described.  In  order  to 
prevent  any  chance  of  water  being  thrown  up  into  the  gas 
bag,  it  is  as  well  to  place  the  bag  on  a  table.    Let  us  sup- 


THE  BOOK  OF  THE  LANTERN. 


pose  that  this  has  been  done,  and  that  everything  is  ready 
for  making  the  gas. 

The  stove  should  be  lighted  and  turned  down  almost  to 
its  lowest  point,  for  it  is  as  well  to  begin  with  a  small 
amount  of  heat,  although  I  believe  that  it  is  the  practice 
of  some  workers  to  begin  with  a  full  heat,  and  to  turn  the 
supply  down  when  gas  commences  to  come  off.  The  tube 
is  joined  to  the  retort  and  to  the  wash  bottle  ;  but  the 
tube  joined  to  the  delivery  end  of  the  bottle  is  for  the 
present  left  free  at  its  other  end.  After  an  interval  of 
about  five  or  six  minutes,  the  water  in  the  wash  bottle 
should  show  by  its  bubbling  that  the  gas  is  being  generated, 
but  those  bubbles  are  not  as  yet  pure  gas,  but  are  partly 
air  which  has  been  contained  in  the  retort,  and  which  is 
expanded  and  driven  out  by  the  heat.  Y»re  must  wait 
some  time  longer,  until  these  bubbles  are  given  off 
with  regularity,  before  attempting  to  fasten  the  open 
tube  to  the  gas  bag  ;  and  before  doing  so  it  is  as  wij!J 
to  apply  the  test  of  the  blown-out  match  to  the  free  end  of 
the  rubber  tube.  If  the  spark  on  the  match  bursts  into 
flame  directly  it  is  applied  to  the  tube,  we  may  be  sure  that 
gas  is  coming  off  in  earnest,  and  we  can  by  a  dexterous 
movement  fasten  the  tube  on  the  tap  of  the  gas  bag,  at  the 
same  time  turning  on  that  tap. 

Everything  should  now  go  on  with  regularity  and  with- 
out attention,  until  the  bag  is  nearly  half  full.  During 
this  time  it  may  be  noticed  that  the  tube  leading  from  the 
retort  will  emit  a  kind  of  bubbling  noise.  This  is  due  to 
water  lodging  there  which  comes  from  the  crystals  of 
potash  in  the  retort.     3y  simply  lifting  this  tube  up,  and 


40 


THE  BOOK  OF  THE  LANTEKN. 


by  giving  it  a  gentle  pinch — for  half  a  second— the  sudden 
ontrnsh  of  gas  into  the  wash  bottle  will  drive  off  any  water 
that  has  settled  there.  When  the  bag  is  half  full  there  is 
generally  a  lull  in  the  operation,  and  no  bubbles  are  seen 
to  agitate  the  water  in  the  wash  bottle  ;  and  this  opportunity 
may  be  taken  for  turning  on  a  little  more  gas,  but  not 
much  more,  for  presently  the  oxygen  will  run  off  with 
redoubled  vehemence,  and  if  too  much  flame  is  applied  to 
the  retort  the  pressure  may  become  too  great  for  the  con- 
nexions, or  the  cork  of  the  safety  valve  may  fly  out.  By 
governing  the  amount  of  gas  supplied  to  the  stove,  the 
emission  of  oxygen  can  be  very  carefully  regulated.  (This 
regulation  becomes  still  easier  if  a  certain  amount  of 
common  salt  be  added  to  the  gas  mixture  in  the  retort. 
This  should  be  done  just  before  the  retort  is  charged.  The 
proportions  are  as  follows  : — 

Chlorate  of  potash     ...        ...        ...     8  parts 

Manganese     ...        ...        ...        ...    2  „ 

Common  salt  ...        ...        ...        ...     1^  „ 

all  by  weight.  When  common  salt  is  thus  added  to  the 
gas  mixture,  the  chlorate  should  be  powdered,) 

When  the  gas  bag  is  full  and  u  as  tight  as  a  drum,"  the 
various  parts  of  the  apparatus  used  in  making  the  gas 
must  be  disconnected,  and  here  some  caution  is  necessary. 
The  first  thing  to  do  is  to  pull  the  tube  from  the  gas  bag 
and  turn  off  the  tap  at  the  same  instant.  Next  remove 
the  tube  from  the  retort,  and  last  of  all  turn  off  the  gas 
supply  from  the  stove.  Why  I  say  that  caution  is  necessary 
here,  is,  because  if  the  gas  is  turned  off  before  the  retort  is 


THE  EOOK  OF  THE  LANTERN. 


41 


disconnected  from  the  wash  bottle,  the  water  in  the  latter 
may  rush  back  into  the  retort  and  cause  a  small  steam 
explosion. 

This  has  certainly  never  happened  to  me ;  but  I  have 
heard  of  cases  where  such  a  thing  has  occurred,  and 
although  it  would  probably  be  unattended  by  any  serious 
results,  it  might  lead  to  a  great  deal  of  mess  and 
trouble. 

The  retort  may  be  left,  until  it  has  become  nearly  cold, 
or  at  any  rate  until  it  is  cool  enough  to  be  handled.  The 
branch  pipe  should  then  be  unscrewed,  and  the  retort  at 
once  washed  out  with  water — warm  water  by  preference. 
This  should  be  thoroughly  done,  and  many  changes  of  water 
should  be  used,  until  the  last  wash  water  comes  away  per- 
fectly clean.  If  the  retort  is  left  with  the  residue  of  the  gas 
mixture  in  it,  the  metal  inside  is  very  quickly  corroded,  and 
the  vessel  does  not  last  half  so  long  as  it  does  if  it  be  at 
once  carefully  washed.  The  branch  and  the  india-rubber 
connecting  tubes  should  be  washed  out  also. 

I  have  mentioned  that  the  commercial  chlorate  of  potash 
is  contaminated  with  a  certain  amount  of  free  chlorine.  This 
soon  renders  itself  evident  if  the  operator  places  his  nose 
near  the  delivery  tube  from  the  wash  bottle  when  the  gas 
is  coming  off ;  for  chlorine  gas  has  a  suffocating  odour. 
This  is  not  the  only  disadvantage  which  it  has  in  gas 
making  for  lantern  purposes,  for  it  so  acts  upon  the  india- 
rubber  bag  and  the  attached  brass  work  that  it  quickly 
leads  to  deterioration.  By  placing  in  the  wash  bottle 
water  something  which  will  seize  hold  of  this  chlorine  and 
detain   it,   we  shall   avoid  this   last  difficulty,  and  the 


42 


THE  BOOK  OF  THE  LANTERN. 


best  substance  for  the  purpose  is  caustic  soda,  or 
potash..  Failing  this,  common  washing  soda  will  answer 
nearly  as  well.  Caustic  soda  is  rather  an  awkward  thing 
to  travel  about  with,  for  it  is  of  a  most  corrosive  nature  ; 
but  it  should  be  used  in  preference  to  anything  else,  when 
gas  is  made  at  home.  Fragments  of  disused  lime  cylinders 
will  also  answer  well. 

To  show  that  the  chlorine  is  actually  taken  up  by  the 
bag  and  its  belongings,  I  may  mention  that  if  the  experi- 
ment be  tried  it  will  be  found  that  the  gas  when  first  made, 
although  highly  charged  with  chlorine  and  inducing 
coughing  and  other  unpleasant  sensations  if  inhaled,  may, 
after  having  been  left  in  the  bag  for  an  hour  or  two,  be 
breathed  without  any  ill  effect. 

Mr.  Fleuss,  whose  diving  and  life-saving  apparatus  de- 
pends in  a  great  measure  upon  a  supply  of  compressed 
oxygen  gas,  called  my  attention  to  the  above  fact,  and  told 
me  that  he  had  used  gas  for  breathing  purposes  which  had 
been  freed  of  its  chlorine  by  remaining  in  the  gas  bag  for 
some  hours  as  I  have  just  explained. 

I  may  mention  that  the  residue  left  in  the  retort— and 
which  I  have  recommended,  should  be  washed  out  without 
delay,—  consists  of  chloride  of  potash,  and  the  manganese ; 
the  latter  quite  unaltered.  It  may  be  useful  to  point  out 
that  the  difference  between  the  chlorate  and  the  chloride  is 
easily  seen  by  examining  the  crystals  of  each  under  a 
microscope.  If  a  little  chlorate  mingled  with  water  is 
placed  on  a  slip  of  glass,  and  allowed  to  evaporate,  the 
crystals  will  have  a  rhombic  form  (see  A,  fig.  19).  But  if,  on 
the  other  hand,  a  solution  of  chloride  of  potash  be  examined 


THE  BOOK  OF  THE  LANTERN. 


43 


in  the  same  manner,  they  will  be  found  to  be  square  in  out- 
line, as  in  B.  Should  it  be  desired  to  use  the  manganese 
over  again,  it  must  be  freed  from  the  chloride  by  repeated 


changes  of  water.  It  will  thus  be  dissolved  out,  while  the 
manganese  remains  behind  in  the  form  of  black  mud. 
This  latter  must  be  dried  before  being  again  employed  in 
the  retort. 

The  operation  of  oxygen  gas  making  is  now  with  many 
lanternists  a  thing  of  the  past,  for  they  prefer  to  buy  it 
ready  made.  For  many  years  this  gas  has  been  supplied, 
by  one  or  two  makers,  compressed  in  iron  or  steel 
cylinders.  But  the  price,  eightpence  per  foot,  was  too 
high  to  induce  consumers  to  relinquish  the  custom  of 
making  it  themselves.  Of  recent  months,  however,  the 
gas  has  been  supplied  at  half  that  price,  with  the  result  that 
many  prefer  to  buy  it  rather  than  make  it  themselves. 
The  manufacture  of  oxygen  gas  therefore  represents  "  A 
curious  new  industry,"  and  under  that  title  I  described  it  a 


Fig.  19. 


44 


THE  BOOK  OF  THE  LANTERN. 


short  time  ago  in  an  article  in  "  Chambers's  Journal."  From 
that  article  I  will  now  give  the  following  extract : — 

"  Any  manual  of  chemistry  will  inform  us  that  oxygen 
is  the  most  widely -diffused  element  in  nature.  It  enters 
into  the  composition  of  air,  of  water ;  it  is  found  in  nearly 
all  earths  and  rocks ;  and  forms  more  than  one  half  of 
animal  and  plant  life.  In  fact  it  is  not  too  much  to  say 
that  oxygen  forms  one -half  of  the  globe  and  its  belongings  ; 
but  of  course  it  is  combined  with  other  elements.  Chemists 
can  tell  us  of  a  dozen  different  methods  of  isolating  this 
gas  ;  but  the  one  most  usually  adopted  is  to  subject  a  salt  of 
potash  (potassic  chlorate),  which  is  extremely  rich  in 
©xvgen,  to  heat  in  a  retort,  when  it  quickly  parts  with  that 
gas,  which  can  be  collected  in  a  suitable  containing  vessel 
for  use.  To  show  the  extent  to  which  this  salt  is  used  for  the 
production  of  oxygen,  we  may  mention  that  we  were  lately 
informed  by  a  London  dealer  that  he  sold  yearly  one 
hundred  tons  of  potassic  chlorate,  and  that  he  had  reason  to 
believe  that  it  was  nearly  all  used  for  the  production  of  gas. 
This  quantity  of  the  salt  would  afford,  roughly  speaking, 
nine  hundred  thousand  cubic  feet  of  oxygen,  and  we  must 
not  forget  that  this  is  the  amount  dispensed  through  one 
dealer  only.  The  natural  question  which  arises  as  to  what 
purposes  this  gas  is  applied,  we  shall  deal  with  presently. 
We  have  preferred  to  show,  first,  that  there  is  an  enormous 
demand  for  oxygen,  so  that  the  importance  of  a  new 
industry  for  producing  it  may  be  at  once  appreciated. 

"  Oxygen  forms  one-fifth  of  the  air  which  we  breathe,  the 
other  four-fifths  consisting  of  an  inert  gas  called  nitrogen. 
And  it  is  important  that  we  should  remember  that  the 


THE  BOOK  OF  THE  LANTERN. 


45 


mixture  of  these  two  gases  is  a  strictly  mechanical,  not  a 
chemical  one.  What  we  mean  is  this.  If  it  were  possible 
by  any  means  to  make  visible  and  magnify  the  particles  of 
air,  we  should  be  able  to  distinguish  the  atoms  of  oxygen 
and  of  nitrogen  side  by  side,  but  in  the  proportion  of  one 
to  four.  It  might  be  compared  to  a  mixture  of  pepper  and 
salt,  which,  although  it  looks  gray  to  the  unaided  sight, 
would,  under  the  microscope,  show  plainly  the  independent 
grains  of  both  constituents.  (It  is  curious  to  note  that  a 
chemical  mixture  of  the  two  gases,  in  which  their  atoms 
combine  to  form  a  new  compound,  produces  that  useful 
anaesthetic,  nitrous  oxide — laughing  gas.)  It  has  long 
been  the  dream  of  chemists  that  oxygen  might  be  produced 
direct  from  the  atmosphere  by  separating  its  atoms  from 
the  atoms  of  nitrogen  with  which  it  is  associated  but  not 
combined.  Indeed,  a  plan  by  which  this  could  be  accom- 
plished has  long  been  known,  but  it  happens  to  be  one  of 
those  numerous  methods,  which  in  theory  are  perfect,  but 
which  when  reduced  to  practice  are  found  to  be  encumbered 
by  various  difficulties.  But  as  a  new  industry  is  founded 
upon  the  process  referred  to,  and  its  success  has  been 
assured  by  a  patient  conquest  of  the  numerous  practical 
difficulties  associated  with  it,  we  cannot  do  better  than 
describe  it. 

"  It  was  long  ago  demonstrated  by  Boussingault  that  when 
the  substance  called  baryta,  otherwise  the  oxide  of  barium, 
was  heated  to  a  low  redness,  it  would  absorb  oxygen  from 
air  submitted  to  it.  He  further  showed  that  if  this  com- 
pound were  then  raised  to  a  higher  temperature,  the 
oxygen  thus  absorbed  would  be  given  off  once  more,  and  the 


46 


THE  BOOK  OF  THE  LANTERN. 


baryta  would  be  restored  to  its  former  condition,  ready 
for  a  repetition  of  the  action.  It  would  thus  seem  that 
there  was  at  hand  a  process  for  obtaining  from  the  atmo- 
sphere an  endless  supply  of  its  essence,  so  to  speak.  But, 
as  we  have  before  hinted,  theory  and  practice  are  two 
different  things.  The  process  would  not*  work  on  a  com- 
mercial scale.  All  went  well  at  first ;  but  for  some  reason 
or  other,  the  baryta  lost  its  power  of  recovery,  and  would 
not  repeat  its  office  of  absorbing  oxygen. 

"  A  few  years  ago,  two  of  M.  Boussingault's  pupils,  Messrs. 
A.  and  L.  Brin,  resolved  to  carry  through  a  series  of  ex- 
periments to  find  out,  if  possible,  why  in  this  case,  practice 
would  not  endorse  theory.  They  soon  found  that  the  reason 
why  the  baryta  lost  its  power  of  absorbing  oxygen  was  due 
to  certain  molecular  changes,  which  ceased  to  occur  if 
the  air  supplied  was  absolutely  free  from  impurities,  and  if 
the  heat  employed  for  reducing  the  baryta  to  its  first 
condition  were  kept  within  certain  limits.  They  further 
found  that  the  necessary  temperature  might  be  much 
reduced  if  the  material  were  heated  in  a  partial  vacuum. 
Another  advantage  was  found  in  supplying  the  air  under 
pressure,  in  which  case  the  absorption  of  oxygen  from 
it  was  much  increased.  These  new  conditions  were  speedily 
realised  in  apparatus  which  was  erected  in  Paris,  and  which 
for  three  years  yielded  oxygen  of  the  purest  description 
without  any  renewal  of  the  baryta  with  which  the  retorts 
were  charged  at  the  commencement  of  operations  ;  and  this 
apparatus  was  exhibited  at  the  Inventions  Exhibition  at 
South  Kensington  a  few  years  ago. 

"  The  process  having  thus  been  shown  to  be  workable,  the 
inevitable  Company  was  formed ;  and  oxygen  can  now  be 


THE  BOOK  OP  THE  LANTERN. 


47 


obtained  in  any  quantity  at  a  cheap  rate  by  any  one  who 
requires  it.  Brin's  Oxygen  Company  has  established  ex- 
tensive works  at  Westminster,  where,  by  a  system  of 
retorts  and  air-pumps,  the  business  of  abstracting  oxygen 
from  the  air  is  continuously  carried  on.  The  gas  is  carried 
to  a  holder,  in  which  it  is  stored ;  and  is  drawn  from  that 
holder  and  compressed  in  steel  cylinders  for  the  use  of  the 
Company's  customers.  These  cylinders  are  so  strong,  that 
one  having  the  capacity  of  little  more  than  a  cubic  foot  of 
gas  will  hold  forty  feet  when  that  gas  is  compres  ed  within  it. 
These  bottles,  placed  in  wooden  cases,  are  now  sent  over 
the  kingdom  by  rail  and  carrier." 

The  gas  is  of  the  utmost  purity,  and  is  largely  used  for 
charging  water  for  drinking  purposes,  as  a  remedy  for 
certain  diseases. 

The  following  table  gives  the  sizes  of  the  cylinders 
supplied,  together  with  their  length  and  weight : — 

Solid  Drawn  Steel  Cylinders  Charged  to  120 
Atmospheres. 


Cubic 
Contents  in 
feet. 


3 
6 
12 
40 
80 
100 


Diameter 
in 
inches. 


4 

H 
51 


Length 

in 
inches. 


7 
11 

20 
30 
60 
78 


Weight, 

case 
included. 


lb. 

9 

>> 

15 

?> 

43 

» 

72 

>> 

84 

48  THE  BOOK  OF  THE  LANTERN. 


Low  Pressure  Cylinders  Charged  to  10  Atmospheres 


Cub.  contents. 

Diameter. 

Length. 

Weight. 

10  ft. 

u  „ 

10  in. 
10  „ 

20  in. 
36  „ 

391b. 

68  „ 

Each  cylinder  is  fitted  with  a  tap  to  regulate  the  flow 
of  gas,  which  tap  has  a  nipple  over  which  the  rubber 
tubing  can  readily  be  drawn.  The 
advantage  of  using  a  bottle  instead  of 
a  bag  in  the  one  point  of  bulk  is  re- 
markable, as  may  be  seen  by  the  above 
table.  Thus,  six  cubic  feet,  which  will 
be  sufficient  for  an  hour  and  a  half's 
entertainment,  is  contained  in  a  re- 
ceptacle about  the  size  of  a  champagne 
bottle,  and  which  can  be  placed  in 
the  empty  lantern-box  during  use. 
The  amount  of  gas  in  a  bottle  can  be 
readily  ascertained  by  the  use  of  a 
proper  pressure  gauge.  In  fig.  20  one 
of  these  cylinders  is  shown  with  the 
regulator  and  pressure  gauge  attached. 
The  latter  is  of  the  form  commonly 
used  on  steam  engines,  and  is  known 
as  Bourdon's  pressure  gauge.  It  depends  for  its  efficiency 
on  the  action  of  internal  pressure  upon  a  curved  tube  of 
oval  section.  The  greater  the  pressure  the  straighter  the 
tube  becomes,  and  this  movement  is  communicated  by 
simple  gearing  to  the  index-finger.  The  following  table 
will  be  found  useful  to  those  who  employ  compressed  gas  :— 


THE  BOOK  OF  THE  LANTERN. 


49 


Table  showing  the  amount  of  gas  in  various-sized 
cylinders,  as  shown  by  gauge.  the  gauge  indi- 
cation is  in  large  type,  and  the  corresponding 
amount  of  gas  in  smaller  type. 


CAPACITY  OF  BOTTLES. 


3  ft. 

6  ft. 

12  ft. 

40  ft. 

80  ft. 

lOOft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

1800-3 

1800-6 

1810-12 

1800—4O 

—  80 

—  100 

1500-21 

1500-5 

1650-H 

1710-38 

—  76 

—  95 

1200—2 

1200-4 

1500-1O 

1620-36 

—  72 

—  90 

900-H 

900-3 

1350-  9 

1530-34 

—  68 

—  85 

600-1 

600-2 

1200-  8 

1440-32 

—  64 

—  80 

300-O* 

300-1 

1050-  7 

1350-30 

—  60 

—  75 

900-  6 

1260-28 

—  56 

—  70 

750-  5 

1170-26 

—  52 

65 

600-  4 

1080-24 

—  48 

—  60 

450-  3 

990-22 

—  44 

—  55 

300-  2 

900-2O 

—  40 

—  50 

150-  l 

810-18 

—  36 

—  45 

720-16 

—  32 

—  40 

630  - 14 

—  28 

—  35 

^40  12 

—  24 

—  30 

450—10 

—  20 

—  25 

360-  8 

—  16 

—  20 

270-  6 

—  12 

—  15 

180-  4 

—  8 

—  10 

90—  2 

—  4 

E 


CHAPTER  IV. 


LIME-LIGHT  JETS,  BAGS,  PRESSURE  BOARDS,  ETC. 


HERB  are  three  forms  of  jets  for  the  lime-light, 
namely,  the  oxycalcium,  the  blow-through,  or 
safety  form,  and  the  mixed  jet.    The  simplest 
of  all  is  the  first  named. 

The  oxycalcium  jet  consists  of  a  spirit-lamp,  which  is 
fed  from  a  little  reservoir  at  the  back  of  the  lantern.  The 
spirit  furnishes  the  necessary  hydrogen,  and  through  its 
flame  a  jet  of  oxygen  is  passed,  and  impinges  upon  a 
cylinder  of  lime  placed  just  at  the  other  side  of  the  wick. 
This  lamp  will  well  illuminate  a  disc  of  about  ten  feet  in 
diameter  with  a  clear,  white  light.  It  has  the  advantage 
of  simplicity,  but  presents  one  difficulty  in  the  circum- 
stance that  the  lantern  must  be  kept  perfectly  level.  If  it 
is  inclined  backwards,  the  spirit  cannot  flow  to  the  point  of 
combustion,  and  if  it  is  inclined  forwards  the  fluid  may 
flow  too  rapidly  towards  the  wick.  In  some  forms  of 
oxycalcium  lamp  this  is  obviated  by  a  special  construction 
of  the  spirit  cistern,  which  is  furnished  with  an  automatic 
valve  for  governing  the  supply  of  fluid  to  the  wick.  The 
wick  will  rapidly  become  charred  if  the  stream  of  oxygen 


THE  BOOK  OF  THE  LANTERN. 


51 


is  allowed  to  impinge  upon  it;  it  should  be  so  adjusted 
that  the  gas  just  escapes  touching  it  •while  passing  through 
its  flame.  This  form  of  lamp  is  sometimes  fitted  with  a 
wick  of  asbestos,  which  well  resists  the  greatest  heat  that 
can  be  brought  against  it.  The  oxycalcium  lamp  is  value 
able  where  no  hydrogen  gas  can  be  obtained,  and,  while 
far  more  powerful  than  a  mineral  oil  flame,  can  hardly  be 
considered  sufficiently  powerful  for  use  in  a  public  lecture 
hall.  It  is  used  in  many  of  the  hospitals  in  conjunction 
with  a  simple  form  of  lantern  for  throwing  light  upon 
patients  during  certain  operations. 

Before  I  reached  the  mature  age  of 
twelve  I  had  made  oxygen  gas  by 
nearly  every  available  method,  and  had 
used  in  this  work  sundry  blacking 
bottles,  ginger-beer  bottles,  gun-barrels, 
and  gas-pipes,  employing  as  gas-bags 
disagreeable  bladders  fresh  from  the 
butcher's.  It  is  a  wonder  to  me  that 
I  was  never  blown  skywards,  but 
blown-up  in  a  figurative  sense  I  often 
was.  It  is  now  my  turn  to  assume  the 
position  of  "stern  parent," but  in  doing 
so  I  soften  towards  the  juvenile  ex- 
perimenter in  memory  of  my  own 
misdeeds.  Perhaps  a  description  of 
my  first  lime-light  jet,  made  at 
the   cost  of   a    few  pence,  of  two  FlG-  21  • 

gasfitters'  blowpipes,  will  answer  the  purpose  better  than 
anything  else,  of  demonstrating  the  principle  of  the  ordi- 

e  2 


52 


THE  BOOK  OF  THE  LANTERN. 


nary  blow- through,  or  safety  jet,  which,  on  the  whole,  is 
the  best  form  of  burner  for  amateurs  to  adopt  (see 
fig.  21). 

A  is  a  piece  of  wood  rounded  off  at  one  side  of  its  upper 
end,  as  shown,  so  as  to  accommodate  its  form  to  the  bent 
blow-pipe,  which  is  marked  O,  for  this  pipe  is  the  conveyer 
of  the  oxygen.  This  is  fixed  in  position  by  loops  of  wire, 
passing  through  holes  in  the  wooden  support.  Upon 
the  other  side  of  this  support  is  bound  in  like  manner 
another  blow-pipe,  which  has  its  fine  nozzle  cut  off.  This  is 
marked  H,  for  hydrogen,  and  is  connected  when  in  use, 
by  means  of  an  india-rubber  tube,  to  the  house-gas  supply. 
The  upper  points  of  these  two  pipes  are  so  adjusted  that 
the  oxygen  gas  will  blow  through  the  flame  from  the  H 
pipe,  on  to  the  lime  cylinder  L.  A  jet  formed  on  this 
principle  has  the  word  "safety"  linked  to  it,  because  the 
two  gases  are  kept  quite  separate  until  they  meet  at  the 
point  of  com  bustion.  Singly,  they  are  innocent  of  harm  ; 
but  mixed,  except  under  certain  precautions,  as  we  shall 
presently  see,  they  form  an  explosive  compound  second 
only  to  gunpowder. 

To  say  that  the  arrangement  thus  described  and  illus- 
trated is  anything  but  faulty  in  construction  would  be 
absurd,  but  I  will  say  that  there  are  many  jets  sold  of 
far  more  pretension  which  give  no  better  light,  and  cost 
as  many  florins  as  this  one  does  pence.  But  as  I  have 
said,  1  have  described  it  as  a  ready  means  of  explaining  the 
principle  of  the  blow-through  jet.  I  have  tried  many 
different  patterns  of  jets,  and  have  selected  the  one  illus- 


THE  BOOK  OF  THE  LANTERN. 


trated  at  fig.  22  as  being  by  far  the  most  perfect  of  any  of 
the  blow-through  type. 


Fig.  22. 

In  selecting  such  a  jet  the  buyer  should  be  careful  to 
see  that  the  orifice  of  the  0  pipe  is  sunk  within  that  which 


1  1  0  CZZ3  

Fig.  23. 

supplies  the  hydrogen,  as  shown  at  M.  In  many  jets  the 
two  pipes  are  brought  to  the  s&me  level,  but  the  form  I 


54 


THE  BOOK  OF  THE  LANTERN. 


illustrate  gives  a  much  better  light,  probably  because  the 
two  gases  are  better  mixed  before  reaching  the  lime.  L  is 
the  pin  upon  which  the  bored  lime  cylinder  rests,  and  it 
can  be  moved  to  or  from  the  jet  by  means  of  the  shifting 
.screw  S.  K  is  a  rod  which  extends  outside  the  lantern, 
and  which  is  for  the  purpose  of  turning  the  lime  cylinder. 
The  form  shown  is  one  commonly  met  with,  and  it  consists 
of  a  rod  connected  with  a  bent  spiral  of  wire.  I  have 
long  ago  discarded  this  arrangement,  as  it  works  by  fitful 
starts,  and  jerks  the  lime  round  instead  of  moving  it  by 
degrees.  The  form  of  lime-turner  attached  to  the  jet 
shown  at  fig.  23  is  the  one  to  select. 

This  form  is  known  as  the  mixed  jet,  by  which  the  most 
powerful  form  of  lime-light  is  obtainable,  but,  as  already 
pointed  out,  it  is  not  so  suitable  as  the  one  before  described 
for  amateur  use.  Both  gases  must  be  under  the  same 
pressure,  therefore  two  bags  for  0  and  H  respectively 
must  be  employed,  usually  under  the  same  pressure  boards. 
The  jet  is  safe  enough  in  skilled  hands,  but  is  not  so, 
unless  care  be  taken  with  every  detail.  The  two  gases 
are  led  to  the  box  or  chamber  W,  where  they  mix,  and 
impinge  upon  the  lime  through  the  single  jet  J.  D  repre- 
sents a  recent  improvement  which  I  believe  was  first 
suggested  by  that  very  good  authority  on  lantern  matters, 
Mr.  Lewis  Wright ;  it  deals  with  the  manner  of  turning 
the  iime  cylinder,  so  that  it  may  not  become  pitted  by  the 
continued  action  of  the  jet  upon  one  spot.  The  primitive 
plan  was  to  open  the  lantern  door  at  frequent  interval*, 
and  to  give  the  hot  lime  a  hasty  touch  with  the  finger. 
Next  the  lime  pin  was  furnished  with  a  screw  which  could  be 


THE  BOOK  OF  THE  LANTERN. 


55 


worked  outside  the  lan  fcern,  so  that  it  was  turned  and  raised 
by  the  same  action.  But,  strange  to  say,  the  screw  was  of 
so  fine  a  pitch,  as  in  fig.  22,  that  by  one  revolution  the 
pitted  part  of  the  lime  was  once  more  brought  under  the 
influence  of  the  jet.  In  Mr.  Wright's  arrangement,  which  • 
I  have  long  ago  adopted,  the  screw  is  a  spiral,  which 
during  one  revolution  raises  the  lime  quite  a  quarter  of  an 
inch.  This  plan  has  still  further  been  improved  upon  by 
the  addition  of  a  nicked  wheel,  which  prevents  the  lime 
being  turned  by  the  operator  more  than  is  necessary  for 
the  time  being.  This  addition  is  known  as  "Newton's 
Improved  Check-action  Lime-movement."  The  same  firm 
of  opticians  have  carried  out  a  still  further  improve- 
ment devised  by  Mr.  Andrew  Pringle.  This  consists 
of  what  is  called  a  "  cut  off,"  and  is  applicable  only  to 
the  mixed  gas  jet.  It  gives  the  operator  the  means  of 
setting  his  jet  so  that  the  gases  are  giving  the  best  pos- 
sible light,  and  then  by  the  turn  of  an  extra  tap  cutting 
them  off,  with  the  exception  of  a  small  supply  of  the 
hydrogen  which  keeps  burning.  He  can,  therefore,  adjust 
his  lights  beforehand,  and  feel,  confident  that  a  turn  of 
the  tap  will  once  more  render  them  at  their  best  at  a 
moment's  notice. 

There  is  certainly  room  for  improvement  in  the  manner 
in  which  lime  jets  generally  are  supported  in  the  lantern. 
A  metal  tray,  sliding  in  grooves,  forms  a  base  board,  at  the 
end  of  which  is  an  upright  rod  of  iron  which,  during  use, 
projects  at  the  back  of  the  lantern.  Upon  this  vertical 
rod  the  whole  jet  can  be  moved  up  or  down,  and  can  be 
clamped  in  position  by  means  of  a  couple  of  screws,  with 


56 


THE  BOOK  OF  THE  LANTERN. 


milled  heads.  The  arrangement  is  by  no  means  a  good 
one,  but  it  is  one  of  those  simple  things  which  have  been 
unheeded  by  the  many,  and  manufacturers  generally  have 
adopted  it  without  perhaps  thinking  how  inconvenient  it  is 
in  practice.  In  the  first  place,  the  jet  is  apt  to  slip  either 
downwards  bodily,  or  to  one  side  or  the  other  by  a  careless 
touch  of  the  operator's  hand.  In  either  case,  such  a  shift- 
ing of  the  light  out  of  the  optical  axis  causes  the  disc  to  be 
darkened  until  the  jet  be  readjusted,  which  cannot  be 
easily  done  without  opening  the  door  of  the  lantern  and 
letting  out  a  flood  of  light  in  the  darkened  room.  There  is, 
besides,  much  trouble  in  getting  the  jet  central,  which  could 
easily  be  avoided  by  a  more  rational  arrangement.  Mr. 
Pumphrey,  of  Birmingham,  has  devised  for  the  purpose  a 
horizontal  and  vertical  rack  motion,  very  like  the  same 
movement  which  is  attached  to  the  mechanical  stage 
of  a  microscope,  but   it   is   somewhat   expensive,  and 


Fig.  24. 


adds  extra  weight  to  the  lantern.  There  is  no  doubt, 
at  the  same  time,   of  its  effectiveness  and  conveni- 


THE  BOOK  OF  THE  LANTERN. 


57 


ence.  A  simpler  plan  is  that  recently  introduced  by  Mr. 
Steward,  and  shown  at  fig.  24.  In  this  case  a  tongue  of 
metal  is  fixed  to  the  supply  pipes  of  the  jet,  and  this 
tongue  has  a  slot  in  its  centre,  which  engages  a  vertical 
pin  on  the  lantern  tray.  This  pin  is  threaded  so  that  a 
couple  of  discs  can  firmly  clamp  the  metal  tongue  when 
the  jet  has  been  once  centered.  Once  clamped  in  this 
way,  the  jet  cannot  be  moved  until  it  is  released  by 
unscrewing  the  discs. 

Another  valuable  improvement  is  represented  by  Wood's 
lime  cylinder  shield,  which  is  shown,  fitted  to  a  jet,  at 
fig.  25.    It  consists  of  a  metal  cylinder,  rather  larger  than 


Fig.  25. 


the  lime,  in  which  the  latter  is  free  to  turn.  There 
is  an  opening  in  front,  through  which  the  incandescent 
lime  can  throw  its  light  towards  the  condensing  lens. 
In  jets,  generally,  the  lime  is  quite  exposed,  and  unless  it 
be  gradually  heated  will  often  crack  to  pieces,  by  the 


58 


THE  BOOK  OF  THE  LANTERN. 


unequal  expansion  which  it  undergoes.  The  shield  pre- 
vents this  by  confining  the  heat  within  a  narrow  area 
around  it,  at  the  same  time  keeping  the  lantern  itself  com- 
paratively cool.  Mr.  Wood  tells  me  that  there  is  an 
undoubted  gain  of  light  from  this  conservation  of  heat  in 
and  around  the  lime  cylinder.  The  shield,  moreover,  does 
much  to  obviate  a  by  no  means  uncommon  accident, 
namely,  the  fracture  of  the  valuable  condenser  itself  from 
a  flame  deflected  towards  it  from  a  cracked  or  much-pitted 
lime  cylinder. 

The  most  general  method  of  storing  the  gases  required 
for  the  lime -light  is  by  means  of  bags,  which  should  be  of 
the  best  quality.  It  is  necessary  to  caution  the  beginner 
on  this  point,  for  I  have  known  cases  where  a  perfectly 
new  bag,  fresh  from  the  maker,  has  been  found,  on  trial, 
to  leak  badly.  I  cannot  say  that  such  an  unpleasant  cir- 
cumstance has  happened  to  myself,  for  I  go  to  a  maker 
upon  whom  I  can  rely.  It  may  possibly  have  been  the 
fault  of  the  operator  himself,  who  did  not  take  the  pre- 
caution to  warm  the  bag  before  use.  For  these  bags  in 
winter  time — when  of  course  they  are  most  generally  used 
— get  stiff  and  hard,  and  if  not  of  good  quality  are  apt 
to  crack,  unless  carefully  warmed  before  use. 

The  best  bags  are  made  of  un vulcanised  rubber,  covered 
on  the  outer  side  with  twill,  and  on  the  inner  side  writh  coarse 
canvas.  This  rough  canvas  serves  a  double  purpose — it 
gives  strength  to  the  bag  and  also  prevents  the  inner  sides 
sticking  together  when  the  bag  is  empty.  After  a  bag  has 
been  in  use  some  time,  the  presence  of  this  canvas  makes 
itself   evident  by  a  quantity  of   fibrous  matter  which 


THE  BOOK  OF  THE  LANTERN. 


59 


comes  out  of  the  jet,  and  which  I  have  been  gravely  told 
by  an  ignorant  operator  is  a  deposit  left  by  the  oxygen 
gas ! 

The  bag  is  furnished  with  a  brass  stop-cock,  which  is 
apt  to  get  so  stiff  as  to  be  very  difficult  to  turn.  For  this 
reason  the  screw  holding  the  plug  of  the  tap  should  be 
undone  frequently,  and  the  plug  touched  with  a  little  oil, 
vaseline,  or  tallow.  This  stiffness  is  due  to  free  chlorine, 
which,  as  is  explained  in  the  chapter  on  oxygen  making, 
is  often  present  in  that  gas.  The  purchaser  of  a  bag  is  of 
course  to  a  great  extent  at  the  mercy  of  the  trader,  and 
many  inferior,  bags  are  sold  to  the  unwary.  But  a  few 
inquiries  among  those  who  know  what  a  good  bag  should 
consist  of  will  soon  inform  the  buyer  where  he  can  pur- 
chase one  which  is  reliable  in  quality.  Certainly  too  rigid 
an  economy  should  not  be  exercised  in  this  particular  part 
of  the  lantern  equipment. 

The  gas-bags  are  made  wedge-shaped  so  that  they 
can  be  placed  between  sloping  pressure  boards  fur- 
nished with  weights.  I  have  heard  of  careless  operators 
who  are  content  to  trust  to  luck  for  finding  suitable 
boards  for  their  gas-bag,  or  bags,  when  they  arrive  at  the 
scene  of  operations.  This  is,  of  course,  a  most  repre- 
hensible proceeding.  But  should  an  exhibitor  be  so  placed 
that  he  cannot  obtain  boards,  a  blackboard,  such  as  can 
be  found  in  any  schoolroom,  can  be  used  for  the  purpose, 
provided  that  it  is  fastened  by  staples  to  the  floor.  It 
must  also  have  a  shelf  at  the  other  end,  on  its  upper  side, 
against  which  the  weights  can  rest.  This  is  but  a  make- 
shift, and  one  which  should  only  be  resorted  to  in  an 


60 


THE  BOOK  OF  THE  LA.NTERN. 


emergency.  In  some  of  my  experimental  lectures,  where 
I  require  a  lime-light  for  occasional  use   on  the  plat- 


Fig.  26. 


form,  I  carry  with  me  a  small  bag  holding  only  three  feet 
of  gas,  and  a  special  form  of  pressure  board  which  I  have 
designed  for  the  purpose.  It  consists  simply  of  two  pieces 
of  inch  board,  each  pierced  on  one  edge  with  corresponding 
Centre-bit  holes  three-quarters  of  an  inch  in  diameter- 
Into  these  holes  fit  half  a  dozen  round  rods  of  pine.  A 
couple  of  pieces  of  wood  screwed  to  the  under  edge  of  one 
of  these  pieces  of  board  serve  as  a  support  to  the  twenty- 
eight-pound  weight  employed.  The  lower  part  of  this 
skeleton  pressure  board  is  furnished  with  a  couple  of  bolts 
which  shoot  out,  and  into  two  screw  eyes,  fastened  to  the 
floor.  The  whole  arrangement  will  be  rendered  clear  by 
the  annexed  sketch  (fig.  26).  I  merely  describe  it  here  in 
the  hope  that  it  may  be  as  useful  to  others  as  it  has  been 
to  myself. 


THE  BOOK  OF  THE  LANTERN. 


61 


For  the  blow- through  jet  only  one  pressure  board  is 
required,  and  perhaps  a  better  form  cannot  be  used  than 
a  couple  of  thin  boards  hinged  together  with  a  simple 
ledge,  or  shelf,  above,  also  on  hinges,  for  the  reception  of 
the  weights.  But  for  the  mixed  jet  another  arrangement 
is  necessary.  In  this  latter  case  the  two  gases  must  be 
under  equal  pressure.  Two  pairs  of  boards,  like  those 
just  described,  may  be  used  side  by  side,  but  they  will 
occupy  a  great  deal  of  space,  and  a  double  supply  of 
weights  will  become  necessary.  This  last  objection  is, 
perhaps,  more  cogent  than  the  first,  for  in  these  days  of 
patent  weighing  machines  the  old-fashioned  56-pounders 
are  becoming  quite  scarce.  It  is,  therefore,  much  better 
to  use  a  pair  of  boards,  so  constructed  that  they  will 
embrace  both  bags — one  set  of  weights  being  all-sufficient 
for  the  two.  A  further  advantage  of  this  arrangement  is 
that  both  bags  are  under  the  same  pressure,  and  additional 
weights  put  on  during  performance  cannot  affect  one  bag 
to  the  prejudice  of  the  other.  Dangerous  accidents  have 
before  now  happened  when  independent  pressure  boards 
have  been  in  use,  from  the  weights  having  been  in- 
advertently shifted  from  one  gas,  while  the  other  has  been 
left  under  full  pressure. 

To  Mr.  Maiden  is  due  the  credit  of  having  first  designed 
a  pair  of  pressure  boards  which  would  hold  both  bags 
under  one  set  of  weights,  and  the  arrangement  which  he 
suggested  is  that  which  is  now  commonly  adopted  by 
opticians,  and  figured  in  their  catalogues.  I  myself 
use  a  modified  form  of  these  pressure  boards,  and 
as  J  have  given  much  thought  to   the  subject  before 


62 


THE  BOOK  OF  THE  LANTERN. 


having  them  constructed,  and  as  they  answer  their  purpose 
most  perfectly,  I  will  describe  them. 

They  are  what  are  called  skeleton-boards  ;  that  is  to 
say,  they  consist  of  frames  filled  in  with  sail-cloth.  This 
mode  of  construction  saves  a  great  amount  of  weight. 
The  wood- work  is  of  best  pine,  1|  inches  thick,  and  is 
mortised  at  every  joint.  Referring  to  fig.  27,  it  will  be 
seen  that  the  upper  frame,  is  furnished  with  a  couple  of 


f  '  N 

1            '     '  1— 

I®  S 

© 

6  <S 

*' 

'•o 

&' 

7 

\ 

Fig.  27. 


Fig.  28. 


hinged  shelves,  between  which  the  weights  are  placed. 
These  shelves  are  made  of  hard  wood,  so  that  they  will 
not  readily  break.  The  lower  frame  (fig.  28)  has  let  into  it 
a  smaller  frame,  which,  when  the  boards  are  not  in  use,  is 
bolted  into  the  main  frame  for  travelling.  But  when  in 
use,  this  lower  frame  is  caused  to  fall  downwards,  so  that 
it  acts  as  a  support  for  the  pressure-boards,  keeping  them 
at  the  right  angle.     The  hinges  which  connect  the  two 


THE  BOOK  OF  THE  LANTERN. 


63 


frames  together  are  of  wrought  iron  and  of  very  solid 
construction  ;  for  they  have  to  bear  some  amount  of  strain. 
It  will  be  noticed  that  the  sail-cloth  is  made  in  two  pieces, 
with  eyelet  holes  along  the  edges  where  they  meet,  so  that 
by  means  of  strong  cord  they  can  be  laced  up  and  rendered 
as  tight  as  a  drumhead. 

Between  the  two  frames  there  is  secured  a  sheet  of  sail- 
cloth, which  is  nailed  down  to  the  lower  board  at  the 
hinged  end.  In  the  centre  of  its  other  extremity  is  sewn 
a  flattened  ring  of  galvanised  iron.  Where  the  sail-cloth 
is  nailed  to  the  woodwork  zinc  roofing  nails  should  be 
used,  for  they  will  never  rust.  To  the  end  of  the 
lower  frame  which  is  farthest  away  from  the  hinges 
is  nailed  a  strong  leather  strap,  about  six  feet  long,  and 
when  the  bags  are  in  position  this  strap  is  passed  through 
the  flattened  ring  on  the  midway  sheet  of  sail-cloth,  and 
then  through  a  corresponding  opening  on  the  upper  frame, 
where  it  is  secured  with  a  buckle.  By  means  of  this  strap 
the  two  bags  are  kept  in  place,  while  the  sail-cloth  sheet 
between  them  also  helps  to  prevent  them  slipping  back- 
wards. 

It  is  customary  to  place  the  hydrogen  bag  below  and  the 
oxygen  one  above,  but  I  am  not  aware  that  there  is  any 
advantage  in  so  doing.  Certainly  I  have  met  with  operators 
who  prefer  to  reverse  their  positions,  and  seemingly  without 
any  disadvantage. 

The  taps  on  the  bags  should  have  a  large  bore,  and  the 
tnbes  which  serve  to  connect  them  with  the  lantern  should 
also  be  of  good  size.  The  amount  of  weight  on  the 
bags  is  governed  to  some  extent  by  the  size  of  disc  re- 


64 


THE  BOOK  OF  THE  LANTERN. 


quired  to  be  shown.  Using  a  disc  of  from  15  to  18  feet  in 
diameter  the  exhibitor  will  do  well  to  commence  when  the 
bags  are  full  with  two  half-hundredweights  on  his  pressure 
boards.  But  when  the  gas  has  been  so  much  used  that  the 
upper  board  gets  nearly  horizontal  the  pressure  will  be 
lessened,  and  the  light  will  suffer  to  some  extent.  When 
this  happens,  the  experienced  operator  will  place  another 
half -hundredweight  in  position,  and  the  increased  bright- 
ness of  the  picture  will  quickly  show  the  advantage  of  so 
doing. 

When  the  gas  or  gases  are  drawn  direct  from  steel 
cylinders,  or  bottles,  if  a  double  or  triple  lantern  is  in 
use,  some  form  of  regulator  must  be  employed.  The  first 
introduced,  and  perhaps  the  most  perfect,  is  that  patented 
by  Messrs.  Oakley  &  Beard. 

Before  proceeding  to  describe  this  important  new  de- 
parture in  lantern  working,  it  may  be  as  well  to  point  out 
one  or  two  difficulties  which  are  incidental  to  the  ordinary 
method  of  storing  the  gases  required  in  india-rubber  bags. 
So  far  as  the  writer  knows,  one  of  these  difficulties  has 
never  been  recognised  in  print.  This  difficulty  is  com- 
prised in  the  fact  that  any  kind  of  gas,  if  kept  in  an  india- 
rubber  bag,  quickly  deteriorates.  By  the  phenomenon 
known  by  the  term  endosmose,  two  gases  separated  by  a 
porous  diaphragm  will  effect  a  mutual  exchange.  Take 
the  case  of  an  ordinary  india-rubber  tube  used  for  a  table 
lamp  or  gas  stove.  How  quickly  it  begins  to  smell. 
This  is  nothing  else  but  the  gas  escaping  through  the 
india-rubber,  and  carrying  on  an  exchange  with  that  other 
gas — the  air — which  is  outside.    It  would  be  interesting 


THE  BOOK  OF  THE  LANTERN. 


G5 


to  know  how  quickly  this  exchange  takes  place  in  the  case 
of  a  bag  of  oxygen;  but,  as  an  experienced  worker,  I 
have  no  hesitation  in  saying  that  there  is  a  marked 
deterioration  in  the  quality  of  the  lime-light,  if  the  oxygen 
gas  used  has  been  kept  for  only  24  hours  in  a  bag 
instead  of  being  freshly  made.  The  same  rule  will 
apply  to  the  hydrogen  gas  in  a  greater  degree,  for  the 
hydrogen  passes  through  a  porous  diaphragm  far  more 
rapidly  than  can  oxygen.  But,  in  practice,  the  H  bag  is 
filled  from  the  nearest  gas-tap  immediately  before  it  is 
wanted.  (Mr.  Fletcher,  of  Warrington,  has  patented  a 
method  of  preventing  the  smell  of  gas-tubes,  by  inserting 
a  partition  of  tinfoil  between  the  two  layers  of  india-rubber 
which  compose  the  tube.  This  foil  stops  the  smell,  by 
stopping  endosmose.  The  same  principle  might,  of  course, 
be  applied  to  gas-bags.  Here  is  a  hint  for  manufacturers.) 
Other  objections  to  the  use  of  gas-bags  are  found  in  their 
initial  expense,  and  the  necessity  for  constant  renewal, 
their  bulk,  and  their  liability  to  mechanical  injury.  In 
spite  of  these  defects,  I  have  always  preferred  to  use  gas 
in  bags,  rather  than  gas  compressed  in  cylinders.  My 
reasons  for  this  choice  I  will  now  give. 

If  the  gases  are  compressed  in  cylinders,  there  is  a 
great  saving  in  trouble,  as  well  as  in  bulk  of  apparatus ; 
but  I  have  hitherto  set  my  face  against  them  for  the 
following  reasons: — 1.  The  pressure  is  so  great,  that  the 
india-rubber  tubes  are  apt  to  blow  off ;  and,  if  tied  on,  may 
burst.  2.  The  light  cannot  be  regulated  at  the  jets  and 
by  the  taps  provided  for  that  purpose,  but  the  taps  must 
be   turned   fully  on,  and  the  outrush  of  gas  roughly 

F 


66 


THE  BOOK  OP  THE  LANTERN. 


regulated — a  very  difficult  matter — by  the  screw  plug  on 
the  nozzles  of  the  bottles.  3.  The  operator  at  the  lantern, 
even  if  he  succeed  in  thus  procuring  the  delivery  of  the 
proper  amount  of  oxygen  and  hydrogen  respectively,  must 
stoop  down  to  do  so,  and,  for  the  time,  neglect  other  duties. 
4.  The  pressure  is  constant ;  and,  therefore,  if  a  double  or 
treble  light  is  suddenly  wanted — as  in  the  case  of  biunial 
and  triple  lanterns  -  the  amount  of  gas  measured  out  for  one 
light,  must  serve  for  two  or  three,  as  the  case  may  be — 
and  all  suffer.  5.  As  the  bottles  gradually  empty,  the 
pressure  sinks;  and,  therefore,  the  screw-plugs  have  to  be 
opened  several  times  during  an  evening's  work.  Every 
time  this  becomes  necessary,  there  is  a  likely  chance  of  too 
much  being  turned  on,  and  the  tubes  being  blown  off.  It 
is,  therefore,  seen  that,  although  bags  are  troublesome, 
bottles  possess  many  disadvantages  which  would  make  any 
careful  operator  pause  before  he  adopted  them.  These 
disadvantages,  however,  entirely  disappear  when  the 
bottles  are  used  with  regulators. 

The  action  of  the  regulator  can  be  understood  without 
much  difficulty  by  reference  to  the  annexed  sectional 
diagram,  fig.  28.  The  screw-thread  ds  at  the  bottom  of  the 
drawing,  is  where  the  casting  D  fits  upou  the  bottle  of 
compressed  gas  ;  dl  is  the  delivery  tube,  governed  by  the 
stop-cock  d2,  B  is  a  base-plate  supporting  the  most  im- 
portant part  of  the  apparatus,  and  E  E  standing  upon  it 
is  merely  a  casing  to  protect  the  enclosed  part  from  injury. 
A  A  are  bellows  made  of  the  finest  rubber,  and  of  a  form 
not  unlike  the  bellows  of  a  camera,  only  that  it  is  circular. 
Th  >  top  of  the  bellows  is  heavily  weighted,  so  that  its 


THE  BOOK  OF  THE  LANTERN. 


67 


natural  tendency  is  to  remain  compressed.  This  top  is 
fnrnished  with  a  collar  C1,  having  a  screw-thread  in  which 
the  screw  pillar  F  can  easily  turn.  It  will  be  noticed 
that  the  thread  of  the  screw  is  coarse,  so  we  may  call 
it  an  Archimedean  screw.     At  its  lower  part  is  a  fine,  and 


Fig.  23. 

therefore  slow-motion  screw,  which  works  in  the  collar  c. 
Now,  let  ns  see  how  beautif nlly  this  donble-screw  motion  is 
applied  to  regnlating  the  delivery  of  the  highly-compressed 
gas.    As  soon  as  the  gas  emerges  from  the  bottle  it  passes 

f  2 


68 


THE  BOOK  OF  THE  LANTERN. 


between  the  space  which  is  open  between  the  valve  f  and 
the  valve  seat  d.  It  then  rashes  into  the  bellows  above, 
which  become  gradually  raised  by  its  pressure.  As  the 
bellows  rise  the  screw  pillar  F  is  quickly  turned  in  its 
socket,  and  gives  a  slow  motion  to  the  screw  below.  The 
effect  of  this  movement  is  to  bring  the  valve  f  down  on  its 
seat  d,  and  the  supply  of  gas  is  cut  off.  But  in  practice 
the  gas  will  be  drawn  off  from  the  delivery  tube  dl  so 
that  the  bellows  will  soon  be  compressed  once  more.  As 
the  bellows  move  downwards,  the  screw  F  acts  in  the  reverse 
manner,  so  that  the  valve  F  is  now  raised,  and  a  fresh 
supply  of  gas  enters  the  bellows.  In  this  way  the  bellows 
are  constantly  rising  and  falling.  If  but  one  lime-light  is 
in  use,  and  the  delivery  of  the  gas  is  therefore  regular, 
the  bellows  will  be  almost  stationary,  for  they  will  auto- 
matically adjust  the  valve  F,  so  that  just  enough  gas,  and 
no  more,  will  pass  through  the  opening.  But  if  two  or 
three  lights  are  in  use,  and  sometimes  only  one,  and  per- 
haps immediately  afterwards  all  three  are  requisitioned, 
then  the  little  bellows  will  have  a  more  lively  time  of  it. 
In  both  cases  the  regulator  will  deliver  the  quantity  of 
gas  which  happens  at  the  moment  to  be  required. 

Some  time  ago  I  contributed  to  The  Camera,  an  illus- 
trated article  showing  how,  by  the  use  of  a  small  gas-bag, 
A,  the  outflow  of  gas  from  a  cylinder  might  be  regulated. 
The  bag  was  in  this  case  made  to  raise  a  lever  as  it 
filled,  thus  cutting  off  the  gas  supply  from  the  bottle,  until 
the  bag  was  partially  emptied,  when  the  action  was  repeated. 
Shortly  after  the  publication  of  this  article  a  self-acting 
valve  on  the  same  principle  was  introduced.    This  valve 


THE  BOOK  OF  THE  LANTERN. 


69 


is  shown  at  fie:.  29.  A  is  the  loose  nut  by  which  it  is 
attached  to  the  gas-bottle ;  B,  the 
valve  proper,  which  is  governed 
by  the  spring  lever  D.  The 
tendency  of  this  sprjng  is  to  keep 
the  bag  shut,  and  when  in  that 
position  the  tap  is  open.  The 
gas  pressure,  however,  quickly 
inflates  the  bag,  and  turns  off  the 
gas  supply.  The  delivery  pipe, 
E,  is  connected  with  the  lantern. 
The  apparatus  is  small  and  com- 
pact, and  works  well. 

It  may  be  noted  here,  that  there  is  a  distinct  gain  in 
using  pure  hydrogen,  instead  of  the  carbureted  gas 
from  the  main,  although  its  employment  undoubtedly 
leads  to  extra  trouble  and  ex- 
pense. The  most  convenient 
way  of  making  this  gas  in  small 
quantities  is  by  treating  scrap 
zinc  with  dilute  acid.  A  con- 
venient apparatus  is  that  shown 
in  the  diagram,  fig.  30.  It  was 
devised  some  years  ago  by  Mr. 
Pumphrey,  and  published  in  one 
of  the  Photographic  Annnals. 
It  consists  of  a  copper  container, 
in  which  is  an  inverted  box  with 
a  delivery  tube  and  tap  attached 
to  it  for  drawing  off  the  gas  as 
it  is  generated.    This  inner  box 


Fig.  30. 


70 


THE  LOOK  OF  THE  LANTERN. 


has  a  removable  perforated  shelf  fitted  to  it,  and  the  box 
itself  is  so  arranged  that  it  can  be  wedged  tightly  in  its 
place.  The  shelf  is  to  hold  the  necessary  supply  of 
scrap  zinc,  and  as  the  acidulated  water  attacks  the 
metal,  hydrogen  is  rapidly  given  off,  until  the  water  is 
forced  by  the  pressure  of  the  gas  below  the  shelf,  and 
the  action  ceases.  It  is  again  renewed  when  gas  is 
drawn  off  from  the  tap,  for  then  the  water  again  rises 
to  the  zinc,  and  a  fresh  supply  is  generated.  This 
apparatus  is  clearly  a  modification  of  the  Dobereiner 
lamp,  in  which  the  gas  generated  in  this  manner  impinges 
upon  and  renders  red-hot  a  pellet  of  spongy  platinum. 
At  a  recent  lantern  exhibition  at  the  Crystal  Palace,  where 
a  30 -foot  screen  was  used,  pure  hydrogen  from  a  bottle 
fed  the  lime-light.  On  one  occasion  ordinary  coal-gas  was 
substituted,  with  a  loss  of  light  which  was  estimated  by 
those  well  qualified  to  form  a  judgment,  at  no  less  than 
25  per  cent. 


CHAPTER  V. 


THE  LIME-LIGHT  AND  ITS  MANAGEMENT. 


[HE  lime-light  was  discovered  about  the  year  1826 
by  Lieut.  Drummond,  R.E.,  during  the  progress 
of  the  Ordnance'  of  Ireland  Survey,  when  the 
want  of  some  method  of  signalling  between  distant  stations 
was  much  felt.  As  originally  constructed,  Drummond's 
lamp  was  very  different  to  the  convenient  forms  of  lime  jet 
now  in  use.  It  consisted  of  a  blow-pipe,  which  impinged 
upon  a  ball  of  lime  about  as  big  as  a  marble.  This  lime 
ball  did  not  last  more  than  half  an  hour,  but  when  spent 
another  took  its  place  automatically.  The  lime  ball  was 
placed  in  the  focus  of  a  parabolic  silvered-copper  reflector. 
With  this  apparatus,  the  light  was  visible  from  Antrim  in 
Ireland,  to  Ben  Lomond  in  Scotland,  a  distance  of  ninety - 
nre  miles  as  the  crow  flies.  Upon  another  occasion,  the 
light  from  the  Drummond  lamp  was  distinguishable  at  a 
distance  of  one  hundred  and  twelve  miles. 

When  manufactured  limes  cannot  be  obtained,  a  piece 
of  limestone  fresh  from  the  kiln  can  be  sawn  roughly  to 


72 


THE  "BOOK  OF  THE  LANTERN. 


the  cylindrical  form,  and  rubbed  down  with,  a  file  ;  or  a 
piece  of  good  hard  chalk  will  serve,  if  there  is  nothing 
better  at  hand.  The  following  mixture  has  been  recom- 
mended as  one  from  which  a  hard  substance  can  be 
moulded  which  will  take  the  place  of  the  usual  lime 
cylinder  : — 

Precipitated  Chalk    4  parts. 

Heavy  Magnesia  Carbonate    1  part. 

Mix  to  paste  with  gum-water,  and  mould  to  form. 

Of  late  years  some  new  limes  have  been  introduced,  with 
the  trade-mark  ' '  Excelsior."  These  will  do  admirably  for 
the  blow-through  jet,  but  will  not  (at  any  rate  in  my 
hands)  withstand  the  attack  of  a  powerful  mixed  jet.  I 
have  always  regretted  that  I  cannot  use  them,  for  they  are 
uniform  in  size,  are  accurately  turned  and  bored,  and  are 
packed  in  a  very  convenient  manner.  A  good  hard 
material  which  will  last  for  several  hours,  and  which  is  not 
affected  by  damp,  is  a  thing  that  is  much  wanted  for  lime- 
light working.  The  following  extract  from  Lieut.  Drum- 
mond's  paper  in  the  Philosophical  Transactions,  1826,  is 
interesting,  as  showing  that  the  discoverer  of  the  lime -light, 
made  trials  of  various  substances,  but  found  lime  to  be  the 
best  : — 

"  The  results  of  several  trials  made  at  the  commencement, 
gave  for — 

Lime   37  times 

Zirconia   31  times 

Magnesia    16  times 

the  intensity  of  an  Argand  burner.    The  oxide  of  zinc  was 


THE  BOOK  OF  THE  LANTERN. 


73 


also  tried ;  but  besides  wasting  away  rapidly,  it  proved 
inferior  even  to  magnesia. 

"  Of  these  substances,  and  also  of  their  compounds  with 
one  another,  lime  appearing  to  possess  a  decided  superiority, 
my  subsequent  experiments  were  confined  to  it  alone,  and 
by  a  more  perfect  adjustment  of  the  apparatus,  by  bringing 
the  maximum  heat,  which  is  confined  within  narrow 
limits,  exactly  to  the  surface  of  the  lime  ball,  and  by  using 
smaller  balls  than  those  employed  in  the  early  experiments, 
a  very  material  increase  of  light  has  been  obtained.  The 
mean  of  ten  experiments,  made  lately  with  every  pre- 
caution, gives  for  the  light  emitted  by  lime,  when  exposed 
to  this  intense  heat,  83  times  the  intensity  of  the  brightest 
part  of  the  flame  of  an  Argand  burner  of  the  best  construc- 
tion, and  supplied  with  the  finest  oil.  The  lime  from  chalk, 
and  such  as  is  known  at  the  London  wharfs  by  the  name  of 
flame  lime,  appears  to  be  more  brilliant  than  any  that  has 
been  tried.  When  well-burned  Carrara  marble  is  made 
into  a  paste  with  water,  and  gradually  dried,  it  appears  to 
be  nearly  equal  to  the  preceding  ;  when  strongly  com- 
pressed, or  very  porous,  it  is  inferior." 

The  best  limes  to  be  obtained  are  of  the  kind  known  as 
"  hard,"  or  "  Nottingham  limes/'  These  last  better  than 
any  others  that  I  know  of.  They  are  sold  in  tin  boxes 
holding  one  dozen  each,  and  are  packed  in  powdered  lime, 
kept  as  far  as  possible  from  the  air.  Let  it  be  remembered 
that  these  limes  will  be  spoiled  by  exposure  to  damp  air. 
By  such  exposure  they  swell  to  double  their  normal  size, 
will  break  the  strongest  box  in  which  they  are  confined, 
and  will,  finally,  fall  to  powder.    In  other  words,  they  are 


74 


THE  BOOK  OP  THE  LANTERN. 


made  of  quick  lime,  and  moisture  will  slake  them.  Lime 
cylinders  are  difficult  things  to  keep,  for  damp  air  will  get 
to  them  in  spite  of  ordinary  precautions.  I  have  tried  to 
preserve  them — with  partial  success — by  dipping  each 
cylinder  separately  into  a  solution  of  indiarubber  in  ben- 
zole or  chloroform,  which  forms  a  skin  upon  its  surface. 
An  American  writer  publishes  a  better  plan.  He  melts 
some  solid  paraffin  or  bees'  wax  in  a.  metallic  vessel, 
exercising  care  that  the  heat  is  just  enough  to  render 
the  substance  liquid  and  no  more.  He  then  dips  each 
cylinder  into  the  wax  half  way,  allows  it  to  cool,  and  then 
holding  it  by  its  waxed  end,  dips  the  other  half.  This 
coating,  he  says,  quite  excludes  the  air,  and  the  limes  may 
be  rolled  in  paper  and  packed  away  until  wanted  for  use. 
The  coating  is  readily  peeled  off  when  the  lime  is  required 
for  the  lantern,  provided  that  the  heat  employed  in  melting 
the  wax  was  not  too  high  when  the  cylinders  were  dipped. 
Each  lime  is  cylindrical,  and  about  one  inch  and  a  half  in 
length,  with  a  central  hole  for  the  reception  of  the  pin 
upon  the  jet.  This  hole  should  be  carefully  freed  of 
powdered  lime,  by  running  a  match  through  it,  after 
which  the  cylinder  can  be  placed  upon  its  pin,  where  for 
the  present  we  will  leave  it. 

As  already  indicated,  the  most  commonly  used  form  of  lime 
jet  is  the  safety,  or  blow-through  kind.  If  the  jet  be  a 
properly-constructed  one,  it  will  well  illuminate  a  picture 
15  feet  in  diameter.  In  this  jet  the  hydrogen  is  sup- 
plied from  the  nearest  household  source,  by  a  connecting 
tube  of  india-rubber.  Herein  lies,  perhaps,  its  only  dis- 
advantage.    In  an  ordinary  house  the  connexion  is  an 


THE  BOOK  OF  THE  LANTERN. 


75 


easy  matter,  but  in  large  halls,  which  are  now  commonly 
lighted  by  one  or  two  sunlights  high  overhead,  the 
operator  finds  himself  in  a  serious  difficulty.  In  this  jet 
the  two  gases  do  not  mix  until  they  reach  the  point  of 
combustion,  and  for  this  reason  the  apparatus  is  dis- 
tinguished by  the  word  "  safety."  For  hydrogen  and 
oxyen,  when  mixed  together,  form  an  explosive  vapour  of 
most  terrible  power,  and  one  which  is  most  difficult  to 
control.  If  any  one  should  wish  to  prove  this,  let  him  fill 
a  soda-water  bottle  with  the  gases  over  a  pneumatic  trough 
in  the  proportions  of  two  volumes  of  hydrogen  to  one  of 
oxygen.  Then  close  the  bottle  with  a  well-greased  cork, 
and,  after  wrapping  it  in  a  towel  in  case  of  fracture,  take 
out  the  cork,  and  put  the  mouth  of  the  bottle  in  front  of  a 
candle  flame.  The  report  caused  by  the  explosion  of  the 
gases  will  be  quite  equal  to  a  heavily-charged  fowling- 
piece.  But  when  the  two  gases  are  used  in  conjunction 
with  the  safety-jet  there  is  no  risk  of  explosion,  for  no 
mixture  takes  place  until  the  gases  meet  on  the  lime 
cylinder.  I  know  that  accidents  have  happened  when 
this  jet  has  been  in  use,  but  they  are  traceable  to  im- 
proper use  of  the  apparatus.  A  case  of  this  kind  came 
under  my  notice  quite  lately.  An  optician  had  employed 
a  new  hand  to  see  after  the  making  of  the  oxygen  gas  and 
filling  the  bag  with  the  same.  This  individual  was,  after 
a  time,  left  to  his  own  devices,  and  finding,  upon  one 
occasion,  that  the  bag  was  not  full,  he  attached  it  to  the 
nearest  gas-bracket  until  it  was  properly  distended.  This 
bag  was  used  in  public  the  same  evening,  and  a  few 
minutes  after  the  proceedings  commenced  it  blew  up,  and, 


76 


THE  BOOK  OF  THE  LANTERN. 


besides  wrecking  the  lantern,  smashed  all  the  windows  in 
the  hall.    The  cause  of  the  disaster  leaked  ont  afterwards. 

But  with  proper  care  this  jet  is  perfectly  safe,  and 
one  which  I  have  used  scores  of  times  for  purposes  of 
demonstration  in  crowded  school-rooms.  As  the  bulk  of 
my  readers  are  more  likely  to  adopt  this  form  of  limelight 
than  any  other,  I  will  give  directions  for  working  with  it 
which  will  at  once  show  its  simplicity.  We  will  suppose, 
in  order  to  make  the  matter  clearer,  that  the  operator  has 
a  single  lantern  fitted  with  this  form  of  jet. 

Beyond  the  mere  lantern  and  its  belongings,  there  will 
be  required  some  india-rubber  tubing,  a  box  of  limes,  and 
a  bag  or  bottle  of  gas.  The  best  rubber  tubing  is  the  red 
variety;  but  it  is  expensive.  It  will,  therefore,  be  found 
economical  to  adopt  a  plan  which  I  myself  have  practised 
with  advantage.  Two  lengths  of  tubing  are  required,  one 
for  each  of  the  gases  employed.  A  6-foot  length  will  be 
sufficient  to  connect  the  0  side  of  the  jet  with  the  iron 
bottle  or  bag ;  but  the  length  of  the  other  piece  of  tubing, 
which  is  to  connect  the  H  side  of  the  jet  with  the  nearest 
house  gas-burner,  is  obviously  dependent  upon  the  distance 
of  that  supply  from  the  place  where  the  lantern  is  being 
exhibited.  If  the  nearest  tap  is  in  another  room,  it  is  best 
to  use  a  length  of  compo.  (lead)  gas-pipe,  which  is  absurdly 
cheap.  Upon  one  occasion  I  remember  drawing  the  gas 
from  another  house  by  such  a  means  of  communication, 
the  pipe  passing  through  two  windows.  But  it  is  only 
upon  rare  occasions  that  such  a  proceeding  is  necessary, 
and  the  worker  is  generally  able  to  find  a  source  of  gas- 
supply  ready  to  his  hand.     When  such  is  the  case,  I 


THE  BOOK  OF  THE  LANTERN. 


77 


recommend  the  employment  of  two  different  kinds  oi 
tnbing.  There  is  a  hard  black  kind,  made,  I  fancy,  in 
France,  but  easily  procurable  in  this  country,  which  wears 
extremely  well,  far  better,  indeed,  than  the  ordinary  grey 
kind.  It  is  cheap  as  well  as  good.  The  only  part  where 
it  seems  to  deteriorate  is  the  end,  where  it  is  being 
constantly  fitted  on  to  the  metal  jet.  This  gets  soft  and 
rough  after  some  time,  a  failing  which  is  easily  remedied 
by  judicious  amputation.  Use  for  each  gas  a  sufficient 
length  of  this  black  tubing,  and  firmly  attach  to  the  end 
of  each  piece  a  short  length  of  the  more  elastic  red  tubing, 
by  which  connexion  with  the  bottle  and  house  gas  respec- 
tively can  be  easily  made.  In  joining  the  two  kinds  of 
tubing  together,  use  a  couple  of  inches  of  lead  pipe  as  a 
connecting  link  between  them.  First  draw  the  black 
tubing  half  way  over  the  lead,  and  then,  if  possible,  allow 
the  red  tube  to  cover  both,  securing  the  whole  with 
string. 

Having  all  these  things  ready,  the  H  tube  fastened  to 
the  nearest  gas  supply,  and  the  O  tube  to  the  bottle  or  bag, 
we  can  proceed  to  work.  Let  the  lime-pin  be  so  adjusted 
that  the  lime  is  about  1-1 6th  of  an  inch  from  the  nozzle  of 
the  jet.  Then  turn  on  the  tap  marked  H,  and  light  the 
jet.  Turn  down  the  gas  until  the  flame  is  about  one 
inch  high,  and  let  matters  thus  remain  for  five  minutes,  to 
give  the  lime  time  to  warm  through  Without  this  pre- 
caution, and  if  the  oxygen  is  turned  on  at  once,  the  lime 
is  apt  to  split  up  from  the  sudden  heat. 

After  this  five  minutes'  rest,  you  may  attend  to  the 
oxygen  supply.    If  the  gas  is  supplied  from  a  bottle  or 


78 


THE  BOOK  OF  THE  LANTERN. 


cylinder  first  turn  the  O  tap  of  the  jet  full  on,  and  let  it 
remain  so.  This  is  a  most  important  point,  and  for  the 
following  reason  :  the  supply  of  oxygen  must  be  regulated 
only  from  the  tap  on  the  bottle,  for  the  pressure  of  gas  is 
so  great  that  if  we  turn  on  the  bottle  tap  and  then  attempt 
to  check  its  now  by  moving  the  tap  jet,  the  connecting 
rubber  tube  will  be  blown  off  or  possibly  split  up.  There 
is  another  advantage  in  keeping  the  hydrogen  jet  burning 
for  some  time  before  the  lantern  is  used.  It  warms  the 
glasses,  and  prevents  that  deposit  of  moisture  upon  them 
which  is  otherwise  always  more  or  less  apparent,  especially 
in  a  crowded  room.  Turn  the  H  tap  until  there  is  a  good 
big  flame  from  the  jet,  and  now  very,  rery  gradually  turn 
the  lever  tap  of  the  bottle.  If  you  do  this  too  quickly,  the 
sudden  mixture  of  O  and  H  at  the  jet  causes  the  light 
to  go  out  with  an  unpleasant  crack.  There  is  really  no 
danger,  but  the  noise  frightens  nervous  people,  who  are 
prone  to  associate  with  lanterns  generally  the  idea  of  being 
blown  skyward.  The  regulation  of  the  two  gases  is  a 
matter  which  is  soon  learned  by  experience,  and  is 'governed 
by  the  appearance  of  the  disc  of  light  obtained  on  the  sheet. 
Move  the  two  taps  until  the  best  effect  is  obtained ;  the 
knack  of  doing  so  is  very  soon  learned. 

Having  seen  that  the  gas  jet  is  burning  well  and  quietly, 
which  is  one  sign  that  all  is  at  it  should  be,  the  next  thing 
is  to  see  that  the  light  is  perfectly  central  with  the  optical 
system.  See  that  the  tray  upon  which  the  jet  is  fixed  is 
withdrawn  so  as  to  leave  a  space  of  about  4  inches 
between  the  light  and  the  condensing  lens.  Raise  or  lower 
the  jet  on  its  supporting  rod,  and  move  it  from  left  to 
right  until  the  flare  of  light  seen  upon  the  sheet  is  as 


THE  BOOK  OF  THE  LANTERN. 


79 


central  as  possible.  When  this  is  the  case,  tighten  the  screw 
or  screws  (and  two  are  better  than  one)  which  hold  the  jet 
on  the  rod,  so  as  to  clamp  it  firmly  in  position.  Now  press 
forward  the  tray,  so  that  the  light  approaches  the  condenser, 
and  this  will  canse  the  sheet  to  become  equally  illuminated 
with  a  sharply- defined  margin  all  round.  Now  place  a 
slide  on  the  stage  of  the  lantern,  and  focus  it  as  sharply  as 
possible.  The  best  way  to  do  this  is  to  set  the  focussing- 
screw  so  that  it  is  at  its  middle  position,  then  focus  by 
sliding  in  and  out  the  flange  into  which  the  objective  is 
screwed.  Get  roughly  the  best  focus  which  you  can  obtain 
by  this  means,  and  then  give  a  finishing  touch  by  means  of 
the  focussing-screw. 

If  a  double  or  biunial  lantern  be  employed,  the  necessary 
operations  will  be  rather  more  complicated,  for  here  we  shall 
have  two  lights,  and  two  optical  systems  to  control  instead 
of  one.  But,  when  once  understood,  the  working  of  a  double 
lantern  is  both  simple  and  easy,  so  much  so  that  on  many 
occasions  when  a  good  assistant  was  not  forthcoming  I  have 
worked  the  lantern  myself  and  lectured  at  the  same  time. 
The  two  lanterns  are  connected  by  means  of  a  dissolving  tap, 
such  as  that  shown  in  fig.  3,  which  is  a  very  good  pattern. 
This  tap  is  so  arranged  that  when  the  lever  is  upright  both 
lanterns  have  their  full  supply,  of  the  gases ;  when  the 
lever  is  turned  over  towards  the  left-hand  side,  the  lower 
lantern  only  is  provided  for,  whilst  when  in  the  reverse 
direction  the  upper  one  is  supplied  with  gas.  The  original 
plan  for  dissolving  was  to  move  a  couple  of  serrated 
screens  to  and  fro  in  front  of  the  lenses,  both  jets 
continuing  burning  during  the  entire  exhibition.  The 
more  modern  method  of  cutting  off  the  gas  supply  from 


80  THE  BOOK  OF  THE  LANTERN. 

each  lantern  alternately  has  the  great  merit  of  saving 
nearly  half  the  gas  bill.  It  will  be  noticed  in  the  cut  of 
the  dissolving  tap  that  it  is  furnished  with  two  small  stop- 


cocks, which  are  fixed  on  vertical  tubes  near  its  centre. 
These  tubes  are  by-passes  which  allow  a  small  quantity 
of  gas  to  pass  to  each  burner,  although  the  lever  has 
shut  off  the  main  supply.  The  necessity  for  this  arrange- 
ment is  obvious ;  without  it  the  lantern  not  in  actual  use 
would  be  totally  extinguished.  In  using  the  blow -through 
form  of  jet  both  by-passes  must  be  employed,  but  with 
the  mixed  jet  the  hydrogen  by-pass  only  is  necessary. 
The  first  thing  to  be  done  in  operating  with  a  double 
lantern  is  to  light  the  hydrogen  in  both  lanterns,  and  to  so 
adjust  the  by-pass  that  it  will  admit  just  enough  gas  to 
the  lantern  not  in  use  to  give  a  flame  about  half  an  inch 
high.  When  the  blow -through  jet  is  used  the  correspond- 
ing oxygen  tap  must  be  manipulated  to  furnish  just  enough 
of  that  gas  to  tinge  the  hydrogen  flame.    If  this  precaution 


THE  BOOK  OF  THE  LANTERN. 


81 


be  not  taken,  the  sudden  influx  of  oxygen  to  the  burner, 
when  the  dissolving  lever  is  turned,  will  almost  infallibly 
3ause  the  flame  to  snap  out  with  a  sharp  crack. 

The  mixed  jet  is  as  easily  worked  as  the  safety  form  and 
— despite  the  confidence-inspiring  name  of  the  latter — is, 
in  my  opinion,  quite  as  safe  in  careful  hands.  In  some 
forms  of  mixed  jets  pumice-stone  chambers,  receptacles 
charged  with  discs  of  wire-gauze,  and  other  arrangements 
"which  are  supposed  to  prevent  the  flame  passing  back 
through  the  tubes,  form  part  of  the  design.  I  look  upon 
such  contrivances  as  mere  obstacles  to  the  free  passage  of 
the  gas;  and,  although  some  of  my  jets  were  originally 
provided  with  them,  I  did  away  with  them  as  quickly  as 
possible. 

The  dissolver  for  a  triple  lantern  is  naturally  more  com- 
plicated ;  but  taps  haTTe  been  devised  which  are  so  arranged 


Fig.  33. 

that  any  one  of  the  three  lanterns  can  be  put  in  or  out  of 
action  at  will.     Such  a  tap  is  shown  at  fig.  33.  Another 

G 


82 


THE  BOOK  OF  THE  LANTERN. 


pattern  of  very  compact  form  is  illustrated  at  fig.  34.  In 
this  case  the  by-passes  are  governed  by  taps  which  are 
adjusted  by  the  operator  with  a  screw-driver.  This  seems 
to  be  a  good  arrangement,  as  there  is  no  chance  of 
accidental  turning  off  or  on  by  a  careless  touch,  as  may 
happen  when  the  by-pass  taps  are  exposed. 


Fig.  34. 

There  are  one  or  two  methods  of  manufacturing  oxygen 
gas  for  the  limelight  as  fast  as  it  is  used,  and  although, 
for  reasons  which  I  shall  presently  give,  I  cannot  recom- 
mend such  a  procedure,  the  methods  are  ingenious  enough 
to  warrant  notice.  In  Chadwick's  apparatus  there  is  an 
iron  gas-holder,  which  forms  the  support  of  the  lantern. 
Associated  with  it  is  a  special  form  of  retort  heated  by  a 
Bunsen  burner,  and  charged  with  chlorate  of  potash  and 
manganese  made  up  into  a  cake  previously.  The  operator 
starts  with  a  full  gas-holder,  and  at  the  end  of  perhaps 
fifteen  minutes,  when  it  is  nearly  empty,  lights  the  Bun- 
sen  burner,  and  in  a  few  minutes  enough  gas  is  generated 
to  fill  it  once  more.  The  retort  is  now  charged  with  a 
fresh  cake  of  mixture  ready  for  once  more  filling  the  gas- 
holder as  it  sinks. 


THE  BOOK  OF  THE  LANTERN. 


83 


Another  plan  was  originated  some  time  ago  by  Mr. 
Beseler,  of  New  York,  and  published  by  him  in  one  of  the 
American  journals.  In  this  case  the  mixed  chemicals  are 
placed  in  a  metal  tube,  with  a  Bunsen  burner  beneath  it. 
As  the  gas  is  generated  it  fills  a  small  gasholder,  which 
supplies  the  lantern.  Only  one  part  of  the  tube  at  a  time 
is  subjected  to  he  it,  so  that  when  a  fresh  supply  of  oxygen 
is  wanted,  all  that  is  necessary  is  to  shift  the  Bunsen 
burner  to  another  part  of  the  tube,  and  the  gasholder  is 
replenished.  This  latter  plan  is  more  simple  than  Chad- 
wick's  ;  but  I  object  to  both,  unless  it  be  for  experimental 
work  at  home,  on  two  broad  grounds.  One  is,  that  the 
blow-through  jet  can  only  be  used  in  conjunction  with 
such  an  apparatus,  and  the  other  is,  that  a  lantern  operator 
has  quite  enough  to  do  in  attending  to  his  burners  and 
changing  the.  pictures  without  being  burdened  with  the 
constant  anxiety  of  seeing  to  the  gas  supply. 

Of  late  years  much  has  been  heard  about  the  so-called 
ether-oxygen  or  ethoxo  limelight,  so  called  because  the 
vapour  of  sulphuric  ether  is  used  in  lieu  of  the  ordinary 
hydrogen,  or  coal-gas.  I  have  tried  this  light,  and,  while 
admiring  its  brilliance,  which  is  quite  equal  to  any  form 
of  limelight  which  I  have  seen,  I  am  very  doubtful  as  to 
its  safety.  I  have  no  doubt  that  it  can  be  so  arranged  as 
to  work  with  safety ;  but  several  explosions  which  have 
occurred  with  it  show  very  conclusively  and  unpleasantly 
that  that  time  has  not  yet  arrived.  With  the  tempting 
advantages  of  extreme  portability  and  brilliant  light 
which  this  or  any  other  system  may  offer,  I  hold  that  it  is 
a  positive  duty  to  eschew  it  until  it  is  known  by  further 

g2 


84 


THE  BOOK  OF  THE  LANTERN. 


experience  to  be  absolutely  innocuous.  Some  may  say, 
"  Oh,  there  is  no  real  danger ;  the  worst  that  can  happen 
is  one  of  the  tubes  blowing  off  with  a  bang  !  "  But  this 
apparently  harmless  "  bang "  may  cause  a  panic  in  a 
public  hall,  which  may  lead,  possibly,  to  fatal  results.  So, 
for  the  present,  at  any  rate,  I  shall  do  without  the  ether 
light,  while,  at  the  same  time  I  shall  look  forward  to  its 
gradual  perfection  with  the  greatest  interest.  It  is  only 
fair  to  state  that  this  light  is  much  used  in  America, 
its  greatest  champion  being  Mr.  Ives,  who  recently  con- 
tributed a  paper  on  the  subject  to  the  Franklin  Institute. 
Mr.  Ives  is  such  a  good  worker  that  his  words  carry  weight 
with  them.  I  quote  the  following  remarks  from  his 
paper : — 

"  Notwithstanding  the  great  success  of  this  means  for 
producing  the  limelight,  and  the  important  advantages 
which  it  offers,  I  have  always  recognised  in  it  certain 
minor  faults,  which  I  hoped  to  overcome  in  course  of  time, 
an<I  my  object  in  preparing  this  paper  has  been  to  call 
attention  to  some  recent  improvements  I  have  made,  which 
I  believe  will  greatly  extend  the  use  of  the  light,  and 
increase  its  popularity.  The  first  improvement  is  in  the 
construction  of  the  saturator,  which  is  reduced  in  size,  yet 
increased  in  effectiveness.  The  second  is  in  the  use  of 
petroleum  ether  (rhigolene),  which  gives  the  same  light  as 
sulphuric  ether,  but  vaporises  at  a  lower  temperature,  costs 
much  less,  and  contains  neither  alcohol  nor  water  to  accu- 
mulate in  the  saturator. 

"My  improved  saturator  is  in  the  form  of  a  single 
metallic  tube,  2  inches  in  diameter  and  13  inches  long, 


TIIU  BOOK  OF  THE  LANTERN. 


85 


with  a  handle  at  the  middle  and  a  stop-cock  projecting  up- 
ward at  each  end.  A  neck,  like  that  of  a  bottle,  projects 
from  the  screw  cap  at  the  end,  and  is  closed  with  a  cork 
for  convenience  in  filling.  The  passage  for  oxygen  is  over 
20  inches  long,  in  the  form  of  a  zig-zag  channel  through 
the  upper  surface  of  the  roll  of  porous  material,  and 
secures  complete  saturation  of  the  gas  with  vapour.  The 
saturator  can  be  filled  from  a  bottle  in  one  minute,  and  is 
ready  for  use  at  once,  or  may  be  kept  filled  for  any  length 
of  time.  Petroleum  ether  costs  only  thirty  cents  a  pound, 
which  is  less  than  half  the  price  of  sulphuric  ether ;  it  also 
vaporises  at  a  lower  temperature,  so  that  the  light  can  be 
used  successfully  even  in  a  very  cold  room,  and  it  has 
other  advantages.  It  will  supply  a  pair  of  lanterns  con- 
nected by  dissolving  key,  for  two  hours  continuously.  It 
should  be  stored  in  a  cool  place  and  kept  tightly  corked. 
It  is  also  necessary,  when  using  it  with  oxygen  from  a 
cylinder,  to  use  a  valve  that  can  be  opened  very  slowly, 
because  a  very  small  amount  of  oxygen  passing  the  satu- 
rator will  produce  a  very  large  flame  at  the  jet.  The 
Shaw  valve,  manufactured  by  Mr.  Shaw,  a  member  of  this 
Institute,  fulfils  the  requirements,  and  is  already  largely 
used  in  this  city.  Some  special  instruction  for  the  manage- 
ment of  the  light  in  hot  weather  may  also  be  called  for. 

"In  conclusion,  I  give  it  as  my  opinion  that  this  im- 
proved means  for  supplying  the  hydrogen  element  is  so 
much  simpler  and  more  convenient  than  any  other,  that  it 
cannot  fail  to  entirely  supersede  the  use  of  hydrogen  and 
coal-gas,  when  its  merits  shall  hare  become  generally 
known  and  appreciated." 


CHAPTER  VI. 


SCREENS. 


NDER  this  head  comes  the  sheet,  hung  in 
the  required  position  by  supporting  cords,  and 
screens  fixed  on  built-up  frames. 
First,  as  to  the  simple  sheet.  A  badly -hung  sheet  is 
an  abomination.  It  should  be  so  hung  that  there  is  a  cer- 
tain pull  upon  it  from  the  centre  to  the  edges  all  round, 
and  this  may  be  brought  about  by  following  the  directions 
now  given.  The  sheet  may  be  made  of  either  linen 
or  cotton.  I  prefer  the  latter,  because  it  is  cheaper,  and 
more  opaque,  and  we  shall  presently  see  that  opacity  car- 
ries with  it  certain  advantages.  If  the  sheet  is  of  such  a 
size  that  it  must  be  joined  (that  is  to  say,  if  it  be  more 
than  about  10  feet  square),  the  necessary  seams  should  lie 
horizontally,  not  vertically.  A  sheet  in  which  the  seams 
are  vertical,  is  liable  to  hang  in  festoon-like  folds  ;  but  if  the 
seams  be  horizontal,  it  will  hang  straight,  so  long  as  its  top 
edge  is  properly  secured.  The  sheet  should  have  along 
this  edge  a  broad  hem,  in  which  is  run  a  strong  cord. 
This  cord  should  be  firmly  fastened  to  the  corners  of  the 


THE  BOOK  OF  THE  LANTERN. 


87 


sheet,  and  in  such  a  way  that  when  it  is  stretched,  the 
material  of  which  the  sheet  is  made  will  not  pucker.  At  each 
end  of  this  cord  there  should  be  a  loop  made  by  doubling 
it  over,  and  wrapping  it  round  with  waxed  thread. 
Along  each  side  of  the  sheet  should  be  placed,  at  intervals 
of  about  eighteen  inches,  galvanized  iron  rings,  or  brass 
curtain  rings  will  answer  the  purpose.  The  bottom  of  the 
sheet  may  be  left  free. 

A  screen  of  this  description  will  require  no  fittings  to 
hang  it  in  position,  beyond  a  couple  of  screw-eyes  placed 
so  far  apart  that  the  sheet  will  easily  go  between  them  ; 
and  which  should  be  inserted  in  the  cornice  or  roof  of  the 
exhibition-room,  with  two  more  eyes  placed  immediately 
underneath  the  top  ones,  and  screwed  into  the  floor.  Next 
are  required  two  strong  but  thin  cords ;  and  it  is  best  at 
the  outset  to  procure  these  of  the  best  quality  possible,  for 
upon  their  strength  the  sheet  entirely  depends.  Each  cord 
should  be  fitted  at  one  end  with  a  swivel  and  clip  like  that 
upon  a  dog's  chain. 

Having  made  these  preparations  the  hanging  of  even  a 
large  sheet  will  be  comparatively  easy.  First,  let  the  cords 
be  run  through  the  fixed  screw-eyes  in  the  roof  or  upper 
part  of  the  wall ;  one  cord  through  each  eye,  and  so  inserted 
that  the  clips  on  the  cords  are  inside, — i.e.,  facing  each 
other.  Next  clip  the  sheet  to  the  cords  by  the  loops  pro- 
vided at  the  top  corners,  as  already  described.  The  sheet 
can  now  be  pulled  up  bodily, — preferably  by  two  persons, 
one  at  each  cord.  Next  place  the  free  ends  of  the  cords 
through  the  screw-eyes  in  the  floor,  and  stretching  the  sheet 
as  tightly  as  possible,  secure  each  by  a  simple  knot. 


88 


THE  BOOK  OF  THE  IANTERN. 


We  shall  now  see  the  advantage  of  the  eyelet-holes  or 
rings  at  the  sides  of  the  sheet.  Fastening  a  piece  of 
string  to  the  top  eyelet-hole  at  one  side, — and  this  is  better 
done  before  the  sheet  is  pnlled  into  position, — allow  that 
string  to  embrace  the  supporting  cord,  next  let  it  pass 
through  the  nearest  eyelet-hole,  then  again  round  the  cord, 
and  so  on  until  the  bottom  of  the  sheet  is  reached.  By  this 
lacing  method  the  sheet  can  be  rendered  almost  as  flat  as  a 
board,  and  presents  the  best  possible  kind  of  surface  so  far 
as  a  sheet  can  give  it  for  showing  lantern  pictures  well. 

Some  little  judgment  must  be  exercised  as  to  the  best 
position  for  the  upper  screw-eyes.  Of  course,  in  practice, 
difficulties  are  apt  to  occur.  The  best  position  may  be  one 
which  the  ladder  available  will  not  reach.  Again,  it  is 
often  the  case  that  screw-eyes  may  be  found  already 
in  position,  and  the  owners  of  public  halls  have  a  righteous 


Fig.  35.         A  B 


objection  to  holes  being  made,  even  to  the  tiny  ones 
necessary   for  fresh  screw-eyes.    In  such  a  case  the 


TUE  BOOK  OF  THE  LANTERN. 


89 


exhibitor  must  content  himself  with  existing  arrangements. 
Bnt  supposing  that  he  has  a  free  will  in  the »  matter,  he 
must  exercise  his  judgment  with  regard  to  the  size  of  the 
hall,  and  the  best  position  for  hanging  a  sheet.  For  in- 
stance, in  a  hall  with  a  pointed  roof,  the  position  A  (see 
figure  35)  would  be  preferable  to  position  B.  In  some 
halls,  again,  the  walls  may  be  so  far  apart  that  the  sheet 
will,  when  hung  in  the  manner  described,  drop  consider- 
ably by  its  own  weight,  so  that,  although  the  screw-eyes 
may  be  20  feet  from  the  ground,  the  top  edge  of  the  sheet 
will  be  only  14  or  15  feet  above  the  floor.  The  best 
way  of  obviating  this  is  by  the  use  of  two  wooden  struts, 
or  supports,  placed  as  shown  in  figure  36.    In  this  dia- 


Fig.  36. 


gram  the  dotted  lines  indicate  the  position  which  the  sheet 
would  occupy  without  this  help. 

The  material  of  which  the  screen  or  sheet  is  made  is  of 
far  more  importance  than  would  be  thought  by  an  inexperi- 
enced worker.  A  careful  artist  knows  that  a  good  picture 
cannot  be  produced  on  crumpled  or  dirty  paper ;  and  the 
lantern  exhibitor  should  be  quite  as  careful  to  provide  for 
his   pictures   an   unblemished   and  even  surface.  Un- 


90 


THE  BOOK  OF  THE  LANTERN. 


doubtedly  the  best  thing  of  all  is  a  simple  white -washed 
wall.  Why  should  this  be  so  ?  Let  me  endeavour  to 
explain  the  matter  in  a  few  words. 

Suppose  that  we  go  behind  an  ordinary  linen  or  cotton 
sheet,  while  lantern  pictures  are  being  thrown  in  front  and 
upon  it.  We  not  only  see  the  picture  distinctly  through 
the  sheet,  but  there  is  enough  light  round  about  us  to  enable 
small  print  to  be  read  with  ease.  At  least  such  is  the  case 
with  the  lime-light,  and  in  a  minor  degree  with  the  oil 
lantern.  Now  all  this  light  means  so  much  deducted  from 
the  light  available  from  the  lantern,  and  which,  therefore, 
is  completely  lost  to  the  spectators  in  front.  From  an 
opaque  wall,  on  the  other  hand,  the  light  is  nearly  all  reflected 
to  the  spectators'  eyes ;  and  although  no  doubt  some  must 
be  absorbed,  we  know  that  none  is  actually  transmitted 
through  the  screen,  and  utterly  wasted,  as  in  the  case  of  a 
semi-opaque  sheet.  We  might  compare  the  two  cases,  to  a 
vessel  of  water  with  a  porous  bottom,  which  will,  of  course, 
allow  a  large  portion  of  the  liquid  to  dribble  through  and 
be  lost ;  as  against  a  vessel  with  a  solid  bottom  which  will 
hold  water  without  any  wasteful  transmission.  But  a 
white-washed  wall  is  not  often  met  with  in  a  lecture -hall, 
and  the  best  substitute  is  a  canvas  sheet  rendered  opaque 
with  white-wash.  Such  a  sheet  is  portable  up  to  a  certain 
size  ;  and  if  intended  for  use  as  a  fixture  in  any  one  hall, 
can  be  made  up  to  any  size,  within  reasonable  limits. 
Witness  the  scenes  on  rollers  at  our  large  theatres  and  opera 
houses,  the  basis  of  which  is  simply  whitened  canvas.  Such 
a  plan  was  adopted  at  the  late  Polytechnic  Institution,  where 
the  screen  measured  no  less  than  26  feet  across. 


THE  BOOK  OF  THE  LANTERN. 


91 


There  is  a  further  advantage  connected  with  using  a 
sheet  of  this  description,  which  is  that  when,  not  in  actual 
use  it  can  be  rolled  up,  and  will  keep  perfectly  clean  for 
many  years.  When  soiled,  a  fresh  coat  of  white-wash  can 
be  given  to  it  with  little  trouble  and  expense.  For  home 
use  a  screen  of  this  nature  is  to  be  greatly  recommended. 
Let  me  now  describe  the  method  by  which  such  a  surface 
can  be  prepared,  and  the  best  way  of  hanging  it  in  position. 
The  following  detailed  directions  are  quoted  from  an  article 
upon  the  subject  which  I  wrote  some  time  back  : — 

Having  decided  upon  the  dimensions  of  the  screen, 
which,  of  course,  must  be  governed  by  the  size  of  the 
room  in  which  it  is  to  be  hung,  we  must  first  of  all  have  a 
frame  made  upon  which  the  material  can  be  stretched 
whilst  being  painted.  Any  kind  of  close- textured  material 
will  answer  our  purpose,  good  unbleached  calico  being  as 
suitable  as  anything  else.  The  frame  should  be  strong, 
for  as  soon  as  the  sheet  is  wetted  it  shrinks,  and  is  apt  to 
pull  an  ill-constructed  frame  all  askew.  The  calico, — if 
joined,  should  be  neatly  sewn, — and  so  tacked  on  the  frame 
that  the  seam  or  seams  will  lie  horizontally.  The  sheet 
must  be  nailed  on  the  frame  with  tacks,  and  this  appa- 
rently simple  work  must  be  done  in  a  certain  way,  or 
it  will  be  pulled  into  creases.  The  four  corners  must 
be  first  secured,  and  afterwards  the  sides  may  be  nailed 
down,  one  side  being  completely  nailed  before  another  is 
begun.  By  this  means  the  sheet  will,  when  done,  present 
one  even  surface.  This  done,  it  must  receive  a  coat- 
ing of  size.  The  best  double  size  should  be  used,  and 
should  be  melted  in  a  suitable  vessel  with  its  own  weight 


92 


THE  BOOK  OP  THI  LANTEEK. 


of  water.  The  size  while  on  the  fire  should  be  watched 
and  occasionally  stirred,  but  should  not  be  allowed  to  boil. 
When  melted,  this  size  is  well  brushed  into  the  calico,  and 
allowed  to  dry.  It  will  then  be  ready  to  receive  its 
coating  of  white  paint.  This  consists  of  whiting  which 
has  been  soaked  in  water  until  it  assumes  the  appearance 
of  thick  white  mud.  To  this  strong  melted  size  must  be 
added  until  the  mixture  is  of  the  consistence  of  cream. 
It  can  be  left  now  for  some  hours  until  it  has  become 
perfectly  cold.  At  the  end  of  that  time  it  should  have 
the  appearance  of  very  weak  jelly, — a  jelly  which  can  be 
easily  broken  up  by  the  paint-brush. 

The  frame  being  placed  upright  and  properly  secured, 
the  workman  commences  at  the  top,  working  the  well- 
charged  brush  up  and  down,  and  then  horizontally,  so  as 
to  avoid  leaving  any  lines  upon  the  surface,  until  it  is  all 
covered.  If  the  sheet  be  unusually  rough  in  texture,  it 
will  benefit  by  another  coat  when  the  first  is  dry. 

When  this  painting  operation  is  finished  the  nails  must 
be  drawn  from  the  frame,  and  the  sheet  must  be  tacked 
on  to  a  roller.  This  roller  may  be  hung  like  a  window- 
blind  at  the  top  of  the  room,  and  governed  by  a  cord  in 
the  familiar  manner.  But  if  it  is  of  large  size, — say  12 
feet  across  or  more, — the  roller  is  best  placed  at  the  bottom 
of  the  sheet,  and  made  to  roll  up  by  cords  upon  its  pro- 
jecting ends,  and  pulleys  above  like  the  drop  scene  at  a 
theatre. 

It  has  often  struck  me  as  a  deplorable  oversight  that 
halls  where  lantern  lectures  are  of  constant  occurrence, 
are  not  fitted  with  permanent  roll-up  screens  of  this  kind. 


THE  BOOK  OF  THE  LANTERN. 


93 


I  know  most  of  the  lecture  halls  in  the  kingdom,  but  I  am 
not  aware  of  a  single  one  where  this  arrangement  exists. 
The  lecturer  who  visits  these  places  is  responsible  for 
bringing  his  own  screen,  and  his  assistant  must  fit  it  up, 
an  operation  which  is  sometimes, — owing  to  the  structure 
of  the  hall, — very  troublesome  and  difficult.  A  permanent 
rolled-up  screen  would  obviate  all  this  difficult}7-,  and  would 
add  greatly,  for  the  reasons  already  given,  to  the  success  of 
the  exhibition.  I  can  only  suppose  that  this  is  one  of  those 
.  matters  which  comes  under  the  head  of  everybody's 
business,  and  therefore  nobody  attends  to  it,  or  seeks  to 
remedy  what  I  feel  is  a  mistake. 

We  will  next  consider  the  method  of  hanging  a  sheet  on 
a  portable  frame.  Some  lecturers  adopt  this  plan,  and  if 
they  are  not  afraid  of  adding  to  their  luggage  a  huge 
bundle  of  sticks,  they  certainly  have  the  advantage  of 
being  independent  of  ladders,  staples,  and  all  the  things 
necessary  for  hanging  a  sheet  in  the  ordinary  way.  There 
are  several  descriptions  of  frames  made  for  this  purpose, 
which  are  sold  by  dealers ;  some  are  good,  and  some 
are  very  much  the  reverse,  giving  much  more  trouble 
than  they  are  worth.  Perhaps  the  best  form  of  frame  is 
that  which  is  made  of  round  pine  sticks,  about  4  or  5  feet 
long,  like  broom-sticks,  and  which  fit  to  one  another, — - 
fishing-rod  fashion, — by  means  of  brass  sockets.  The 
corners  of  the  frame  are  represented  by  sockets  mitred,  and 
brazed  together,  see  fig.  37.  Such  a  frame  as  this  is  easily 
put  up.  First  of  all  the  top  pieces  are  socketed  together, 
and  furnished  with  their  corner  pieces  and  one  length  of 
the  wooden  rods.    The  side  pieces  a*e  next  placed  in  their 


94 


THE  BOOK  OF  THE  LANTERN. 


proper  sockets,  and  the  top  portion  of  the  sheet  is  tied  on  by 
tapes.  It  is  reared  up  a  little  higher  by  the  addition  of  two 
more  side  pieces  ;  and  as  this  building-up  gradually  goes  on 
the  sides  of  the  sheet  are  secured  by  tapes  to  the  frame.  The 


Fig,  37. 

bottom  pieces  are  finally  attached  and  the  frame  is  com- 
plete. If  there  is  room  enough  this  operation  of  mounting 
the  sheet  on  its  frame  is  best  performed  when  both  are 
lying  flat  on  the  floor,  otherwise  it  must  be  done  by 
gradually  building  up  the  frame  while  it  is  in  a  vertical 
position.  At  each  top  corner  should  be  fastened  guy 
ropes,  and  these  can  be  secured  to  staples  screwed  into 
the  floor. 

One  advantage  of  a  frame  of  the  above  description  is 
that,  when,  from  the  nature  of  the  hall,  it  must  be  erected 
on  a  platform  at  a  higher  level  than  that  of  the  lantern, 
the  whole  screen  can  be  made  to  incline  forwards,  so  as 
to  bring  its  surface  square  with  the  lens.  With  a  strictly 
vertical  sheet  the  picture  would,  under  such  circumstances, 
be  thrown  out  of  shape  and  out  of  focus. 

Whatever  wood  may  be  chosen  for  the  material  of  the 


THE  BOOK  OF  THE  LANTERN. 


95 


frame,  it  should  be  strong ;  for  if  the  sheet  is  tightly 
stretched,  as  it  ought  to  be,  there  will  be  a  very  heavy 
strain  upon  its  support.  Perhaps  the  best  wood  for  the 
purpose  is  bamboo,  which  combines  the  qualities  of 
extreme  lightness  with  great  strength.  I  believe  that 
bamboo  frames  can  now  be  obtained  commercially. 

The  rule  for  finding  the  correct  distance  between  lantern 
and  sheet  is  to  add  one  to  the  number  of  times  enlargement 
required,  and  multiply  by  the  equivalent  focus  of  the  lens 
used.  If,  for  instance,  a  slide  measures  3  inches,  and  it  is 
desired  to  cover  a  screen  1 0  feet  across,  the  scale  of 
enlargement  is  40  times  :  and  41  times  the  equivalent 
focus  of  the  lens  gives  the  required  distance  between  lens 
and  screen. 

In  order  to  find  the  equivalent  focus  of  a  lens,  it  is  con- 
venient, in  the  absence  of  special  apparatus,  to  proceed  as 
follows : — Focus  upon  a  white  surface  an  image  of  the 
Sun  or  other  distant  object,  taking  care  to  place  the  lens 
axis  as  nearly  as  possible  in  line  with  the  object,  and 
perpendicular  to  the  surface  receiving  the  image.  When 
the  image  is  sharply  focussed,  measure  carefully  the  dis- 
tance between  it  and  the  nearest  surface  of  the  lens. 
Repeat  this  operation  with  the  lens  reversed,  and  measure 
the  distance  to  the  same  surface  as  before ;  in  this  caae, 
the  surface  furthest  away.  The  average  of  the  two 
measurements  thus  obtained  is  approximately  the 
equivalent  focus  of  the  lens. 

I  am  indebted  to  Mr,  Taylor,  of  Leicester,  for  the  fol- 
lowing useful  table : — 


96 


THE  BOOK  OF  THE  LANTERN. 


Table  of  Distances  between  Lens  and  Screen  for 
various  Scales  of  Enlargement,  and  with  Lenses  of 
various  equivalent  focal  length, 


1  § 

o  & 
.  « 

£  g 

4 

5 

6" 

? 

8" 

:  

9 

10" 

11" 

12' 

Focus  of 
lens. 

12 

4'4" 

B'5" 

6'6" 



7'7" 

8'8" 

9'9" 

1016" 

1111" 

13' 

18 

6'4" 

7' IF 

9'6" 

11' 1" 

12'8" 

14'3" 

1510" 

17'5" 

19' 

w 

24 

8'4" 

10'5" 

12'6" 

147" 

16'8" 

18'9" 

2010" 

2211" 

25' 

« 

30 

10'4" 

12'1 1" 

15'3" 

181" 

2  '8" 

23'3" 

2510" 

28'5" 

31 

o 

CO 

36 

12'4" 

15' 5" 

18'6" 

217" 

24'8" 

27 '9" 

3010" 

3311" 

37' 

p 

42 

J4'4// 

l7'4" 

21'6" 

25' 1" 

2S'8" 

32'3" 

3610" 

39/6'/ 

43' 

48 

16'4" 

2oV 

2/6" 

287" 

32'8" 

36'9" 

4' 10" 

4411" 

49' 

54 

18'4" 

22' 11" 

27'6" 

32a" 

36'8" 

41'3" 

4510" 

50V 

55' 

60 

2  '4'- 

25'5" 

30V 

357" 

40'8" 

45'9" 

5010" 

6511" 

61' 

w 

Hi 

66 

22'4" 

27' 11" 

33'6" 

391" 

44'8" 

50'3" 

5510" 

61V 

67' 

72 

24'4" 

30'o" 

36 '6" 

427" 

48'8" 

54'9" 

601  " 

6611" 

73' 

m 

78 

26'1" 

H211" 

39'6" 

46'1" 

52'8" 

5h'3" 

65l<" 

72'5" 

79' 

84 

28'4" 

3/5" 

42'6" 

497" 

56V 

63'9" 

7  10" 

7711" 

85' 

90 

3<>'4>" 

37/1 >" 

45'6" 

631" 

6"'8" 

68'3" 

75'lfi" 

83V 

91 

ffl 

96 

32'4"' 

40'5" 

48'«" 

567" 

64V 

72'9" 

8«/l'  " 

8811" 

97' 

102 

34'47 

42' 11" 

51'6" 

eo'i" 

68'8" 

77'3" 

8510" 

94'o" 

1  3' 

o 

108 

36'4" 

45'5" 

64'6" 

637" 

72*8" 

81V 

9010" 

9911" 

1' 9' 

114 

38'4" 

4711" 

57'6" 

671" 

76'8" 

86'3" 

9510" 

105  5" 

115' 

120 

40'4" 

5u5" 

60'6" 

707" 

80'8" 

90'9" 

10010" 

11  11" 

121' 

p 

CHAPTER  VII. 


THE    PREPARATION    OP    LANTERN    SLIDES,    DIAGRAMS,  ETC., 
WITHOUT  THE  AID  OF  PHOTOGRAPHY. 

EFOKE  it  became  possible  to  use  photography  in 
conjunction  with  the  lantern,  what  are  called 
hand-painted  slides  had  to  be  depended  upon, 
for  they  were  the  sole  pictures  that  could  be  obtained. 
In  those  days  it  was  common  to  use  a  very  much 
larger  picture  for  the  lantern  than  at  present.  Those 
pictures  which  delighted  one  or  two  generations  of  sight- 
seers at  the  old  Polytechnic,  measured  about  eight  inches 
by  five.  Some  of  these  pictures  were  most  elaborate  works 
of  art ;  so  much  so,  that  at  the  sale  of  the  belongings  of 
the  Polytechnic  in  1881,  when  the  Institution  as  a  place  of 
entertainment  was  broken  up,  many  of  these  slides  real- 
ised as  much  as  fifty  shillings  each.  It  is  to  be  feared  that 
such  hand-painting  on  glass  is  now  almost .  a  lost  art,  for 
people  will  not  pay  the  price  which  would  remunerate  a 
competent  artist,  when  they  can  obtain  a  more  perfect 
representation, — as  to  form  at  least, — by  means  of  a  photo- 
graph.   The  slide-painter  of  those  days  used  to  work  both 


98 


THE  BOOK  OF  THE  LANTERN. 


in  water  colour  and  in  oil  colour,  sometimes,  I  believe, 
combining  the  two  methods  in  one  picture;  and  his  first 
proceeding  was  to  draw  the  outline  on  the  glass,  in  black 
pigment,  with  a  very  fine  brush.  Those  who  do  not  wish 
to  dabble  in  photography,  and  who  have  some  artistic  taste 
may  still  adopt  the  same  plan,  and  they  will  find  that  with 
a  little  practice  they  will  be  able  to  draw  with  a  fine  brush 
and  with  a  suitable  pigment,  as  finely  as  they  can  on  paper 
with  a  pen.  The  Japanese  artists, — I  may  mention, — do  all 
their  worF,  and  even  their  writing,  with  a  brush,  and  we 
all  know  their  pictures  are  not  to  be  despised.  It  will 
be  found  that  such  an  outline  is  easier  to  produce  if  the 
glass  be  first  covered  with  a  layer  of  varnish.  Some  use 
a  weak  solution  of  gelatine  in  water,  to  give  the  glass  the 
necessary  surface  for  taking  the  pigment.  A  solution  of 
sugar  has  also  been  recommended  for  the  same  purpose, 
A  still  easier  plan  of  producing  diagrams  of  line  drawings 
without  the  aid  of  photography  is  to  use  sheet  gelatine, 
which  is  sold  for  the  purpose.  This  gelatine  is  placed  over 
the  engraving  or  other  design  which  it  is  wished  to  copy ; 
and  the  lines  are  traced  with  a  sharp  point,  such  as  an 
etching-needle.  Fine  black  lead  is  then  rubbed  over  the 
surface  with  the  top  of  the  finger,  with  the  result  that  the 
black  powder  lodges  in  the  scratches,  but  does  not  adhere 
to  the  smooth  surface.  This  plan  I  look  upon  merely  as  a 
makeshift;  but  I  mention  it  for  what  it  is  worth. 

A  method  by  which  far  better  results  can  be  obtained 
was  published  some  years  ago  by  the  Rev.  Dr.  Dallinger, 
the  eminent  microscopist,  who  has  for  a  long  time  used 
slides  produced  in  the  way  he  describes.    His  plan  is 


THE  BOOK  OF  TITE  LANTERN. 


99 


briefly  this.  He  works  with  a  hard  pencil  on  a  piece  of 
very  finely-ground  glass  ;  afterwards  filling  in  the  outlines 
thus  made  with  water  colours,  and  applying  a  coat  of  var- 
nish so  as  to  give  the  necessary  transparency  to  the  picture. 
This  method  he  brought  before  the  Royal  Microscopical 
Society,  and  the  following  extract  from  his  paper  describes 
the  matter  so  clearly  that  all  will  be  able  to  follow  his 
directions : — 

"  Most  working  microscopists  have  felt  the  necessity,  in 
reading  papers  on  their  work,  of  accurate  illustration. 
These  enlarged  drawings  fail  in  matter  of  detail,  unless 
extravagant  labour  is  expended,  and  considerable  skill 
employed.  Even  then  the  light  of  an  ordinary  lecture 
hall  is  not  enough  to  enable  the  most  distant  of  the 
audience  to  see  them.  It  is  only  by  means  of  the  limelight 
and  transparencies  that  really  useful  illustrations  can  be 
given.  But  here  the  difficulty  is  to  prepare  them  accu- 
rately and  inexpensively.  Photography  cannot  be  employed 
in  all  cases  ;  and  even  where  it  can  be,  it  involves  more 
labour  than  most  microscopists  can  afford.  Drawing  and 
painting  on  glass  in  the  usual  method  is  an  art  that  it  takes 
years  to  learn  \  and  to  employ  one  who  has  learned  it  to 
draw  from  nature  a  highly-magnified  object,  would  be  to 
introduce  unnumbered  errors  of  interpretation,  unless  our 
artist  be  a  microscopist  himself. 

"  I  obviate  all  these  difficulties  by  the  following  method : 
On  finely-ground  glass,  drawing  with  a  black  lead  pencil 
is  as  easy  as  drawing  on  London  board.  I  get  four  inch 
squares  of  glass  to  suit  my  lantern,  carefully  ground  on 
one  side  like  the  focussing  glass  of  a  camera.    Now  with 

h2 


100 


THE  BOOK  OF  THE  LANTERN. 


the  ground  side  up,  the  camera  lucida  may  be  used  with 
this  as  well  as  with  drawing-board,  if  a  piece  of  white 
paper  be  placed  beneath  it,  and  the  object  drawn  in  the 
usual  way.  For  outlining  and  delicate  shading  I  employ 
H  H  H  H  and  H  II  H  pencils ;  for  deep  shadows  I  use 
H  B.  By  a  very  delicate  employment  of  the  pencil, 
shadows  softer  than  can  be  secured  by  lithography  may  be 
made.  The  camera  lucida,  of  course,  is  not  necessary  ;  we 
may  draw  with  the  eye  and  hand  alone.  If  it  be  necessary 
to  put  on  colour  it  may  be  done  cleanly  and  carefully  over 
the  shading  ;  thus  one  layer  of  colour  suffices.  Now  of 
course,  although  we  have  a  perfect  drawing  of  the  object, 
with  all  the  detail  accurately  given,  it  is  not  a  transparency. 
But  we  can  easily  make  it  one  Thin  some  good  pale  Canada 
balsam  with  benzine  to  about  the  consistence  of  eream ; 
and  simply  float  it  over  the  ground  surface  of  your  glass, 
pour  off  till  the  drop  comes  very  sluggishly.  Then  reverse 
the  glass  so  that  the  corner  from  which  the  balsam  was 
flowing  off  be  placed  upward.  Let  the  return  flow  reach 
about  the  middle,  then  reverse  it  again,  and  move  it  in 
several  directions  to  get  the  balsam  level.  This  may  be 
done  with  very  little  practice  so  that  the  surface  shall  be 
undistinguishable  from  glass.  We  have  now  a  perfect 
transparency.  All  that  is  required  is  twenty  four  hours 
for  hardening  (keeping  the  glass  level)  and  then  another 
square  of  glass  fastened  on  to  it  by  strips  of  paper  afc  the 
edges,  with  small  pieces  of  card  at  the  corners  to  prevent 
contact,  and  it  makes  an  admirable  lantern  transparency. 

"For  obtaining  very  fine  points  to  my  very  hard  leads,  after 
cutting  them  very  loner  and  even,  and  grinding  them  on 


THE  BOOK  OF  THE  LANTERN. 


101 


glass  paper,  I  finish  them  on  a  square  of  the  finest  ground 
glass,  and  with  this  beside  one  in  making  a  delicate 
drawing,  a  good,  fine  working  point  may  be  kept  a  long 
while." 

There  is  sometimes  a  difficulty  in  procuring  ground-glass 
fine  enough  for  this  purpose,  and  I  therefore  advise  those 
who  feel  inclined  to  try  this  method  of  producing  lantern- 
slides  to  prepare  the  glass  themselves ;  which  is  somewhat 
tedious,  but  by  no  means  difficult.  Or  should  they  prefer 
it,  they  can  purchase  the  glass  at  certain  photographic 
warehouses,  where  it  is  sold  for  focussing  purposes  in  the 
camera  ;  but  it  is  rather  expensive.  The  following  direc- 
tions will  enable  any  one  to  grind  the  glass  for  himself  : — 

First  of  all,  obtain  a  piece  of  glass  which  is  both  flat  and 
perfectly  free  from  bubbles  and  other  flaws.  Be  careful, 
too,  to  cut  it  to  the  correct  size  at  this  stage  of  the  proceed- 
ings, so  as  to  avoid  all  risk  of  mistake  in  this  direction 
after  it  has  been  ground.  The  glass  is  now  fixed  on  a 
table  or  board  by  means  of  four  pieces  of  wood,  nailed  on 
the  board  or  table  so  as  to  clip  its  four  sides.  These 
wooden  pieces  must  not  be  thicker  than  the  glass  itself. 
Now  procure  a  piece  of  plate-glass  measuring  about  three 
inches  square,  to  act  as  a  grinder.  Failing  this,  a  piece  of 
ordinary  sheet-glass  can  be  employed  ;  but,  as  it  will  not  be 
thick  enough  to  afford  a  proper  hold  for  the  fingers,  it 
should  have  attached  to  it  a  pneumatic  india-rubber  plate- 
holder  to  serve  as  a  handle. 

Now  take  some  flour  emery  and  mix  it  into  a  thin  cream 
with  water.  Put  some  of  this  on  the  glass,  which  you  have 
fixed  to  the  table,  and  place  the  grinder  above  it ;  rub  the 


102 


THE  BOOK  OF  THE  LANTERN. 


latter  over  the  former  with  a  steady  circular  motion,  taking 
care  to  cover  every  part  in  turn.  This  rubbing  should 
be  continued  for  about  ten  minutes,  adding  water  if  the 
two  surfaces  seem  inclined  to  stick  together  too  much,  and 
occasionally  collecting  with  a  knife-blade  the  mud  which 
oozes  out  between  them,  and  putting  it  once  more  in  the 
centre  of  the  under  glass.  At  the  end  of  the  time 
named  the  glass  can  be  lifted  from  the  table,  held  under 
the  tap  for  a  few  seconds  so  as  to  clean  it,  and  care- 
fully examined  by  transmitted  light.  It  will  most  probably 
show  a  fine  grain,  except  in  certain  parts,  which  remain 
clear  as  before.  These  clear  portions  are  depressions  in 
the  surface  of  the  glass,  which  the  emery  has  failed  to 
reach.  The  grinding  operation  must  be  repeated  as  before 
until  on  examination  these  clear  places  have  disappeared. 

It  has  occurred  to  me  that  Dr.  Dallinger's  system  of 
producing  lantern- slides  might  be  modified  with  advantage 
in  the  following  manner.  Coat  the  glass  with  varnish 
which  dries  with  a  mat  surface,  and  practically  gives  the 
same  effect  as  ground-glass  itself.  There  are  several 
recipes  for  such  varnish,  which  is  used  by  photographers  for 
retouching  purposes.  Here  is  one  which  will  be  found 
effectual. 

Ground-  Glass  Varnish. 
Sandarac  ...        ...        ...    90  grains. 

Mastic      ...       ...       ...    20  „ 

Ether    2  oz. 

Benzole     ...       ...        ...       \  to  \\  oz. 

The  proportion  of  benzole  added  determines  the  nature  of 
the  mat  obtained. 


THE  BOOK  OF  THE  LANTERN. 


103 


The  varnish  is  simply  flowed  over  the  glass  and  allowed 
to  dry  cold,  which  it  will  do  in  a  very  few  minutes. 
After  it  is  thoroughly  hardened  it  can  be  drawn  upon 
with  a  pencil  in  the  way  described,  and  can  then  be 
coloured  with  water  colours  tempered  with  ox-gall,  as 
pointed  out.  We  can  now  make  the  picture  transparent  by 
the  addition  of  another  varnish,  which  must  be  of  such  a 
composition  that  it  will  not  dissolve  or  in  any  way  act  upon 
the  surface  already  laid  upon  the  glass.  Such  a  varnish 
would  be  represented  by  one  not  containing  benzine  as  a 
solvent  for  its  gums.  .1  have  not  tried  this  method  myself, 
and  so  cannot  speak  from  experience ;  but  I  do  not  see  any 
reason  why  it  should  not  succeed. 


;    OHAPTEE  VIII. 


PHOTOGRAPHIC  LANTERN  PICTURES  BY  THE  WET  PROCESS. 

[ANTERN  slides  made  by  the  wet  process  are 
certainly  easier  to  produce  than  those  made  by 
any  dry  method.  It  is  a  matter  of  opinion 
whether  these  are  better  in  quality  than  their  rivals  on 
gelatine,  &c,  and  I  know  that  many  believe  that  a  far 
better  effect  is  producible  upon  a  wet  plate  than  upon  a 
dry  plate.  I  myself  am  of  the  contrary  opinion  ;  but  still, 
as  there  may  be  many  who  may  be  inclined  to  try  the  old 
collodion  method,  my  work  would  be  incomplete  if  I  did 
not  give  directions  by  which  such  slides  can  be  produced. 

If  the  negatives  are  of  the  same  size  as  the  lantern 
plate  ;  that  is  to  say,  if  they  consist  of  quarter  plate  nega- 
tives, they  must  be  reproduced  by  contact ;  and  actual 
contact  with  a  wet  collodion  film  is  of  course  out  of  the 
question. 

There  is  a  method  by  which  this  difficulty  can  be  ob- 
viated. Attach  to  the  negative  a  couple  of  strips  of  note 
paper,  3-g-  inches  apart ;  the  collodion  film  can  then  rest 
against  these  paper  supports  by  two  of  its  edges  during 


THE  BOOK  OF  THE  LANTERN. 


105 


the  necessary  exposure ;  but  in  this  case  care  must  be 
taken  that  the  plate  is  thoroughly  well  drained,  for  a  drop 
of  the  silver  bath  solution,  if  allowed  to  get  into  actual 
contact  with  the  negative,  will  inevitably  spoil  it. 

But  those  who  advocate  the  wet  process  for  lantern- 
slide  work  nearly  always  work  from  larger  negatives 
with  the  camera,  and  by  following  the  directions  now 
given  it  will  be  found  that  very  good  results  can  be 
obtained. 

Place  the  negative  to  be  copied  in  a  suitable  frame 
against  the  window.  This  can  be  done  by  fixing  an  ordi- 
nary printing  frame  (with  the  spring  removed)  against 
the  glass,  and  by  covering  up  the  rest  of  the  window- 
panes  with  brown  paper,  or  some  other  opaque  material. 
Then  support  the  camera  on  a  stand  or  table,  exactly  op- 
posite the  negative,  taking  care  that  it  is  square  with  the 
negative  and  carefully  focus  the  image  on  the  ground  glass. 
A  focussing  glass  is  a  very  great  help  in  this  work,  for  the 
image  is  often  so  dimly  illuminated  that  it  is  difficult  to 
ascertain  whether  it  is  sufficiently  sharp  or  not.  With 
regard  to  exposure,  it  is  very  difficult,  in  fact  impossible,  to 
*  lay  down  any  hard-and-fast  line.  I  can  only  say  that 
with  a  negative  of  normal  density  and  with  a  favourable 
light,  the  exposure  should  be  about  one  minute  ;  but  it  is 
of  course  governed  by  the  type  of  lens  used,  and  the  par- 
ticular stop  employed  with  that  lens.  With  a  portable 
symmetrical  of  5 -inch  focus  and  using  No.  4  stop,  the 
exposure  with  a  normal  negative  will  be  about  that  which 
I  have  indicated. 

But  the  great  thing  which  ensures  success  in  this  process 


106 


THE  BOOK  OF  THE  LANTERN. 


is  to  use  a  proper  developer  and  a  bath  which  is  in  the 
right  condition.  This  bath  should  be  an  old  one ;  that  is 
to  say,  not  a  newly  mixed  one, — one,  in  fact,  which  would 
give  very  hard  results  for  ordinary  portraiture. 

It  should  have  a  tmall  quantity  of  nitrate  of  baryta 
mixed  in  it,  say  3  grains  to  the  ounce  of  bath. 

Develop  with  sulphate  of  iron  sat.  sol.      ...  4  oz. 

Methylated  spirit  4  oz. 

Add  these  to  a  Winchester  quart  of  distilled  or  rain 
water ;  and  allow  it  to  stand  in  the  light  for  some  hours, 
next  filter  it  -into  a  clean  bottle,  and  add  4  drops  of 
colocine. 

Just  before  using  this  developer  add  to  it  one  drop  of 
acetic  acid  per  ounce.  This  addition  ensures  a  very  fine 
deposit,  without  it  the  deposit  may  be  granular.  The 
exposure  should  be  so  regulated  that  no  subsequent  intensi- 
fication is  required,  but  if  an  error  of  judgment  should  be 
made  the  image  can  be  strengthened  by  adding  a  drop  of 
the  silver  bath  to  a  little  of  the  developer  and  flowing 
it  over  the  plate.  The  glass  used  should  be  the 
best,  and  quite  free  from  flaws  of  any  kind.  "  Flatted 
Crown  "  answers  this  description.  It  should  be  care- 
fully cleaned  and  albumenised.  The  albumen  should 
be  flowed  over  one  side  of  the  glass  only,  and  it  should 
consisJ  of  the  white  of  one  egg  to  a  pint  of  water,  with 
the  addition  of  one  drop  of  carbolic  acid. 

A  quantity  of  broken  glass  should  be  placed  in  this 
bottle  and  the  whole  shaken  up  into  froth,  left  to  settle  and 
then  filtered  through  cotton  wool.  As  the  plates  are  coated 
with  this  albumen  mixture,  they  should  be  reared  up  to 


THE  BOOK  OF  THE  LANTERN. 


107 


drain,  and  dry  spontaneously  on  a  slip  of  blotting  paper. 
The  best  collodion  to  nse  is  "  Mawson's  Negative  Col- 
lodion." The  plates  should  be  fixed  in  hypo  of  the  usual 
strength,  and  should  the  image  appear  to  be  "  dirty  "  it 
can  be  rendered  clear  by  being  washed  over  with  a  solution 
of  iodine  and  iodide  of  potassium. 

After  fixation  and  after  the  plates  have  been  thoroughly 
washed,  they  may  be  toned  in  a  solution  of  chloride  of 
platinum, — one  grain  to  4  ounces  of  water,  and  they 
should  remain  in  this  solution  until  the  deposit  is  darkened 
throughout. 

Beginners  very  often  fail  in  getting  a  good  tone  from 
platinum,  and  complain  that  instead  of  darkening  the 
image  the  salt  has  the  opposite  effect.  They  are  recom- 
mended in  some  formulae  to  add  nitric  acid  to  the  toning 
bath,  but  this  is  useless  unless  the  platinum  salt  be 
neutralised  in  the  first  instance.  The  proper  mode  of 
procedure  is  to  -break  the  tube  containing  the  platinum 
crystals  (this  chemical,  like  chloride  of  gold,  is  on  account 
of  its  deliquescent  property  always  sold  in  an  hermetically 
sealed  glass  tube)  into  a  certain  quantity  of  distilled  water. 
A  convenient  plan  is  to  break  a  tube  containing  1 5  grains 
into  15  drachms  of  distilled  water :  one  drachm  of  the 
liquid  will  then  represent  one  grain  of  platinum  chloride. 
Test  this  liquid  before  use  with  litmus  paper:  if  it  show  by 
the  paper  turning  red  that  it  is  acid,  we  may  be  quite  sure 
that  it  contains  free  hydrochloric  acid,  which  will  have  a 
bleaching  effect  upon  the  photographic  image.  The  liquid 
must  therefore  be  neutralised  by  the  addition  of  a  few 
grains  of   carbonate  of   soda,  after  which  it  must  be 


108 


THE  BOOK  OF  THE  LANTERN. 


lendered  sufficiently  acid  with  'nitric  acid  to  slightly  redden 
litmus  paper.  If  the  operator  is  careful  to  follow  these 
directions  he  will  have  no  difficulty  in  toning  his  trans- 
parencies with  platinum. 

We  may  summarise  the  order  of  operations  as  follows  : 
Albumenise  the  glass. 
Dry. 

Coat  with  collodion. 

Sensitise  in  silver  bath. 

Expose. 

Develop. 

Fix  in  hypo. 

Wash. 

Clean  with  iodide  solution  if  necessary, 

Tone  with  platinum. 

Wash. 

Dry. 

The  operations  conclude  with  giving  the  film  a  coat  of 
transparent  varnish.  Any  good  varnish  may  be  used,  but 
care  must  be  taken  if  the  slides  are  to  be  subsequently 
coloured,  that  some  varnish  upon  which  turpentine  has  no 
action  be  employed ;  otherwise  the  turpentine  used  in 
colouring  will  most  surely  mingle  with  the  varnish  and 
ruin  the  picture. 

It  is  hardly  necessary  to  add  that  the  operations  of  sen- 
sitising, developing,  and  fixing  the  plate  must  be  conducted 
in  a  non-actinic  (red)  light,  and  that  all  precautions  usually 
taken  in  dealing  with  photographic  chemicals  must  be 
observed.  The  directions  are  written  for  those  who  have 
already  mastered  the  details  of  such  work. 


CHAPTER  IX. 


LANTERN  SLIDES  ON  DRY  PLATES. 

HERB  are  many  dry  collodion  methods  which 
a  were  originally  designed  for  ordinary  nega- 
tive work  in  the  camera,  but  which  have 
]ong  ago  been  superseded  by  the  far  quicker  and 
more  certain  gelatine  process.  Some  of  these  plates, 
however,  although  they  have  been  discarded  for  the 
main  purpose  of  photography,  are  still  used  by  many 
workers  for  the  manufacture  of  lantern-plates  where  great 
speed  is  a  matter  of  secondary  importance. 

For  many  of  these  processes  the  silver  bath  is  still 
required,  the  plate  after  being  sensitised  therein,  being 
flowed  over  with  some  preservative  solution,  the  function 
of  which  is  to  keep  the  pores  of  the  collodion  film  in  such 
a  condition  that  it  will  not  dry  into  a  horny  state,  im- 
permeable to  any  developer  which  may  later  on  be 
applied  to  it.  As  full  particulars  of  these  processes  can 
be  found  in  most  photographic  text-books,  I  shall  content 
myself  with  giving  here  only  a  brief  survey  of  them, 
reserving  details  of  working  for  the  more  modern  methods 
of  producing  lantern-slides  on  gelatine  plates. 


110 


THE  BOOK  OF  THE  LANTERN. 


Many  of  these  old  processes  differ  only  in  the  kind  of 
preservative  fluid  applied  to  them,  and  from  the  nature 
of  this  preservative  they  usually  are  named.  Thus  we 
have  the  Tannin  process,  the  Honey  process,  the  Coffee 
process,  &c.  Taking  the  first  named,  let  me  cite  it  as  an 
example  of  the  others. 

The  glass -plate  which  is  to  bear  the  picture  is  first  of  all 
carefully  cleaned.  It  is  then  edged  with  india-rubber 
solution,  albumen,  or  some  other  body  which  will  prevent 
the  film  from  slipping  off  the  glass  during  subsequent 
operations.  Next  it  is  coated  with  ordinary  negative 
collodion,  to  which  two  grains  per  ounce  of  bromide  of 
cadmium  may  be  advantageously  added.  It  should  now 
be  dipped  in  a  silver  bath  which  has  been  made  distinctly 
acid,  by  the  addition  of  a  few  drops  of  nitric  acid.  After 
thus  sensitising  the  plate,  it  must  be  well  washed  to  remove 
all  free  silver,  after  which  the  preservative  is  applied, — 


After  the  plates  are  dry  they  are  ready  for  use,  but  will 
only  remain  good  for  a  week  or  two. 

In  another  process  which  gives  good  results  coffee  is  used 
as  the  preservative.  In  this  case  the  bath  can  be  made 
very  acid,  by  the  addition  of  one -fifth  of  its  volume  of 
glacial  acetic  acid.  The  plate  is  edged,  and  sensitised  in 
the  bath,  and  is  then  flowed  over  with  an  infusion  of 
ground  coffee,  After  drying,  these  plates  will  keep  for 
some  months,  and  will  give  fine  results.  The  development 
is  brought  about  by  a  plain  solution  of  pyrogallic  acid, 


Tannin 

Distilled  water 


•  •  • 


35  grains. 
4  ounces. 


THE  BOOK  OF  THE  LANTELIN. 


Ill 


say  two  grains  to  the  ounce  of  water,  and  is  afterwards 
strengthened  by  citric  acid  and  silver. 

A  far  greater  importance  is  attached  to  the  next  method 
under  disscussion,  by  which  the  very  finest  results  can  be 
obtained ;  but  it  requires,  at  every  stage  of  the  process, 
such  great  care  that  few  in  these  days  care  to  take  it  up. 
Still  it  has  a  commercial  importance,  and  is  known  as  the 
Albumen  process.  Here  is  a  sketch  of  the  operations  in- 
volved in  it. 

After  the  plate  of  glass  has  been  rendered  chemically 
clean  it  is  coated  with  a  film  of  albumen  from  fresh  eggs, 
to  which  has  been  added  some  iodide  and  bromide  of 
potassium.  The  plate  is  then  inverted  on  its  pneumatic 
holder,  and  revolved  by  means  of  a  vertical  cord  attached 
to  the  bottom  of  that  holder,  so  that  by  centrifugal  force 
some  of  the  albumenous  coating  is  scattered,  leaving  the 
thinnest  possible  film  on  the  glass.  The  plate  is  then 
dried, — as  yet  insensitive  to  light.  Next  it  is  immersed 
in  an  acid  silver  bath  for  about  three  minutes,  and  after 
washing  with  several  changes  of  water,  a  preservative 
consisting  of  a  saturated  solution  of  gallic  acid,  is  applied 
to  it.  Drying  by  gentle  heat  completes  the  manufacture 
of  this  form  of  plate.  The  development  is  brought  about 
by  a  saturated  solution  of  gallic  acid,  to  which  has  been 
added  a  few  drops  of  silver  nitrate. 

C0LL0DI0-BE0MIDE  PROCESS. 

We  will  now  give  our  attention  to  the  beautiful 
Collodio -bromide  process,  a  brief  description  of  which  is 
only  necessary,  for  the  collodion  emulsion  for  the  lm- 


112 


THE  BOOK  OF  THE  LANTERN. 


mediate  coating  of  the  plates  can  be  bought  ready  made, 
with  full  instructions  for  coating  and  development. 

This  rr.ethod  yields  results  which  cannot  easily  be  beaten. 
It  was  introduced  about  twenty  years  ago  by  Messrs, 
Bolton  &  Sayce,  and  a  number  of  good  workers  have 
since  taken  it  up  successfully.  As  its  name  implies,  a 
collodion  is  employed  containing  bromide  of  silver,  and 
although  many  might  be  deterred  from  attempting  it,  from 
the  fancied  difficulties  which  it  presents  ;  yet,  in  practice 
it  is  by  no  means  a  complicated  process  to  work.  It  has 
certainly  a  great  many  advantages.  When  the  sensitised 
collodion  is  once  compounded  it  will  keep  for  a  long  time. 
Plates  can  be  coated  with  it — a  dozen  at  a  time  if  required 
— and  after  being  dried  by  artificial  heat  are  ready  for 
immediate  use.  When  the  printing  from  the  negative  has 
been  performed,  these  plates,  after  development  and  a 
minute's  washing,  can  be  dried,  and  the  slides  are  finished 
and  ready  for  the  lantern. 

A  plain  collodion  is  first  of  all  made  with  high  tempera- 
ture Pyroxyline,  and  the  usual  solvents,  ether  and  alcohol. 
To  this  is  added  ammonium-bromide  and  citric  acid.  The 
silver 'is  now  dissolved  in  as  little  water  as  possible,  and  is 
added  to  the  bromised  collodion.  The  emulsion  is  then  set 
aside  to  ripen  for  some  hours,  is  poured  out  into  a  dish  for 
the  solvents  to  evaporate,  and  is  then  broken  up  into  small 
pieces  and  washed  in  several  changes  of  water,  so  as  to  get 
rid  of  the  soluble  salts  which  are  not  required.  All  these 
operations  are,  of  course,  conducted  in  non-actinic  light. 
When  these  pieces  have  been  finally  drained  as  closely  as 
possible,  they  are  once  more  dissolved  in  the  requisite  pro- 


THE  BOOK  OP  THE  LANTERN. 


113 


portions  of  ether  and  alcohol,  and,  after  filtering,  the  re- 
constructed emulsion  is  ready  for  coating  the  plates.  They 
can  be  developed  by  a  weak  alkaline  developer  with  pyro, 
or  by  the  ferrous -oxalate  method,  which  will  be  described 
later  on,  Mr.  W.  Brooks,  of  Reigate,  has  made  a  study 
of  this  process,  and  supplies  the  emulsion  ready  made. 
Messrs,  Mawson  and  Swan  have  also  lately  advertised  it, 
so  that  it  is  hardly  worth  while  for  the  worker  to  make  it 
for  himself, 

WOODBURYTYPE  PROCESS. 

This  method  yields  results  which  cannot  be  sur- 
passed, but  it  may  be  looked  upon  more  as  a  com- 
mercial process  than  one  suited  to  the  amateur  worker, 
for  it  necessitates  the  use  of  expensive  plant.  I  shall 
therefore  dismiss  it  with  a  somewhat  brief  description, 
albeit  my  chapters  on  slide-making  would  hardly  be  com- 
plete without  it,  In  the  first  place  a  relief  is  obtained  by 
employing  gelatine,  containing  one  of  the  bichromates  of 
the  alkalies — bichromate  of  potash,  for  instance.  This 
relief  is  placed  upon  a  sheet  of  lead,  and  after  the  two 
have  been  fixed  in  a  steel  frame,  they  are  submitted  to 
hydraulic  pressure,  with  the  curious  result  that  the  tender 
gelatine  film  preserves  its  delicate  outlines,  but  the  leaden 
plate  gives  way,  and  these  markings  are  pressed  into  it, 
This  leaden  plate  then  forms  a  mould  of  the  future  picture, 
its  deepest  parts  representing  the  shades  of  that  picture, 
and  its  higher  parts  the  lights.  This  is  placed  in  a  special 
press,  and  a  pool  of  gelatinous  ink  (made  by  dissolving  any 
suitable  pigment  in  a  warm  solution  of  gelatine  and  water) 

I 


114 


THE  BOOK  OF  THE  LANTEKN. 


is  poured  upon  the  mould.  The  square  of  glass  which  is 
to  bear  the  picture  is  placed  on  this  pool  of  ink,  and  the 
press  is  lightly  brought  down  upon  all.  The  slide  is  left 
thus  until  the  gelatine  has  had  time  to  set,  when  the 
glass  is  lifted  from  the  mould,  and  the  picture  in  all  its 
delicate  details  is  left  upon  it.  This  beautiful  process, 
which  may  be  looked  upon  as  the  most  perfect  of  all  the 
mechanical  photographic  processes,  was  due  to  the  genius 
of  the  late  Mr.  Woodbury,  who,  shortly  before  his  lamented 
death,  modified  it  so  that  it  might  be  practised  by  ama- 
teurs, 

This  modification  is  known  as  the  Stannotype  pro- 
cess, tinfoil  being  employed  as  a  substitute  for  the  work  of 
the  hydraulic  press.  The  gelatine  relief  is  attached  to  a 
plate  of  glass  by  a  suitable  cement,  Its  surface  is  then 
coated  with  india-rubber  cement,  and  a  sheet  of  ordinary 
tinfoil  is  placed  above  it.  The  whole  arrangement  is  now 
passed  between  a  couple  of  india-rubber  rollers,  such  as 
are  attached  to  a  domestic  wringing-machine,  so  that  the 
tinfoil  is  forced  into  the  interstices  of  the  picture,  We 
thus  obtain  a  metallic-faced  mould  without  the  interven- 
tion of  the  hydraulic  press,  and  this  mould  is  afterwards 
treated  with  warm  gelatinous  ink,  and  prints  taken  off,  as 
in  the  Woodburytype  process.  In  the  latter  process,  how- 
ever, a  negative  is  employed  to  give  the  necessary  relief, 
and  in  the  Stannotype  a  positive.  Both  of  these  methods 
give  the  best  results  for  pictures  where  there  is  not  a  large 
expanse  of  sky,  or  other  high  light;  for  in  such  a  case 
a  slight  deposit  of  the  pigmented  gelatine  is  likely  to  spoil 


The  book  of  the  lantern. 


115 


the  transparency  of  such  lights,  and  in  a  good  lantern  slide 
they  should  be  represented  by  clear  glass, 

TRANSPARENCIES  ON  COMMERCIAL  GELATINE  PLATES. 

For  some  inscrutable  reason,  it  used  to  be  the  common 
opinion  among  those  who  ought  to  know  something  about 
the  matter,  that  the  gelatine  process  is  unsuitable  for  lan- 
tern transparencies.  The  introduction  lately  of  gelatine 
lantern  plates  into  the  market  has  done  much  to  correct 
this  error  ;  but  still  there  are  numerous  persons  who  hold 
to  the  belief  that  the  ordinary  gelatine  plate,  such  as  is 
used  for  negative  work,  will  not  produce  a  good  trans- 
parency. For  years  I  have  proved  the  contrary,  and  with 
regard  to  the  quality  of  the  transparencies  produced,  I  have 
seen  few  to  equal  them. 

The  first  operator  who  turned  out  successful  work  of  this 
character  was  Mr.  Kennett,  who  has  the  greater  honour 
of  being  the  first  to  make  gelatine  plates  a  marketable 
commodity.  His  method  of  working  was  to  employ  a  slow 
plate,  to  expose  it  under  a  negative  in  a  printing  frame  for 
the  fraction  of  a  second  in  daylight,  or  for  a  longer  time 
by  lamplight,  and  to  develop  by  either  the  alkaline  or 
ferrous  oxalate  method.  The  plate  was  afterwards  flooded 
with  pyro  and  silver  and  toned  with  gold. 

The  introduction  of  chloride  plates,  which  give  beautiful 
effects,  may  deter  some  from  trying  what  can  be  done  by 
ordinary  gelatino -bromide  plates.  But  for  the  amateur 
whose  time  is  otherwise  occupied  during  daylight,  the  latter 
process  has  many  advantages.    The  chief  one  is  that,  while 

I  2 


116 


THE  BOOK  OF  THE  LANTERN. 


the  exposure  of  a  chloride  plate  to  lamplight  will  occupy 
about  three  minutes,  a  bromide  plate  can  be  successfully 
exposed  in  less  than  three  seconds,  so  that  a  number  can 
be  exposed  in  an  hour  or  two. 

I  have  already  pointed  out  how  a  reduced  positive  can 
be  readily  obtained  from  a  negative  by  means  of  the 
camera.  I  will  now  suppose  that  the  negative  from  which 
the  transparency  is  to  be  taken,  is  on  a  ^  plate,  and,  there- 
fore, the  right  size  for  the  lantern  slide,  and  that  the  pic- 
ture is  to  be  printed  by  contact  in  a  printing  frame. 
The  requirements  are  a  red  lamp,  a  gas  or  paraffin 
lamp,  which  can  be  readily  turned  up  and  down,  and  a 
frame. 

As  in  most  photographic  operations,  correct  exposure  is 
the  main  consideration,  but  whereas  where  daylight  is 
concerned,  this  exposure  is  always  difficult  to  hit  upon, 
because  the  light  varies  so  much  under  different  circum- 
stances ;  here,  where  we  have  a  lamp  to  work  by,  we  can 
measure  its  duration  to  a  nicety. 

I  may  mention  here  that  there  is  a  form  of  gas-burners 
sold  which  is  very  useful  in  this  work.  It  is  fitted  with  a 
bypass,  so  that  it  is  never  actually  turned  out.  A  blue 
bead  of  light  remains,  which  is  quite  shielded  from  view, 
and  this  permanent  flame  ignites  the  full  amount  of  gas 
when  the  stop-cock  is  turned  on.  The  operation  of  print- 
ing a  transparency  consists  in  placing  the  negative  in  the 
frame,  and  placing  upon  it,  film  to  film,  a  gelatine  plate, 
measuring  3^  x  3J  inches.  The  frame  is  closed,  and  is 
h  eld  j  within  a  short  distance  of  the  lamp,  which  is  turned 


THE  BOOK  OF  THE  LANTERN. 


117 


up  for  a  brief  period,  and  then  turned  down  to  darkness 
once  more.  But  how  must  this  period  be  measured  ?  In 
order  to  answer  this  question  I  must  call  attention  to  a 
certain  optical  law  which  I  have  attempted  to  put  in  the 
form  of  diagrams  : — 


Fig.  38. 


Fig.  38  illustrates  the  manner  in  which  the  light  rays 
from  a  candle  strike  out  all  round  it  like  the  spokes  of  a 
wheel ;  but,  for  simplicity  sake,  the  rays  in  one  direction 
only  are  shown.  Let  A  represent  our  printing  frame  held 
at  1  foot  from  the  light  source,  and  let  us  suppose  that 
at  that  distance  the  plate  contained  in  it  will  require  one 
second's  exposure.  Now  let  us  expose  a  similar  plate  at  B, 
which  is  2  feet  from  the  light  source,  what  exposure  will 
it  require?  "Two  seconds,"  the  tyro  will  probably 
answer ;  but  he  would  be  wrong,  the  plate  at  double  the 
distance  will  require  four  times  the  original  exposure ;  at 
treble  the  distance,  nine  times  the  original  exposure.  In 


118 


THE  BOOK  OF  THE  LANTERN. 


other  words,  "  the  intensity  of  illumination  on  a  given  sur- 
face is  inversely  as  the  square  of  its  distance  from  the  source 
of  light." 


Fig.  39. 


Fig.  39  will  perhaps  make  the  matter  still  more  plain.  At 
1  foot  from  the  candle  the  square  marked  i  receives  a 
certain  amount  of  light ;  at  II,  that  light  is  spread  over  a 
surface  four  times  the  area  of  the  first ;  and  at  in  over  a 
surface  nine  times  as  large  as  I.  This  law,  which  is  really 
of  a  very  simple  character,  the  operator  should  have  con- 
stantly in  his  mind,  as  he  exposes  his  plates  to  artificial 
light  under  a  negative. 

The  method  of  development  which  I  recommend  is  by 
means  of  ferrous  oxalate,  and  it  will  be  found  that  the 
transparencies  produced  by  it  require  no  toning  whatever. 
I  make  my  own  potassic  oxalate,  and  find  it,  moreover, 
reliable ;  the  operation  is  simplicity  itself.  In  a  large 
basin  dissolve  half  a  pound  of  carbonate  of  potash  (salts  of 
tartar)  in  a  pint  and  a  half  of  warm  water.  Now  add 
gradually  oxalic  acid,  a  few  crystals  at  a  time,  for  the 
effervescence  is  very  violent,  and  difficult  to  control  if 
much  be  put  in  at  once.    When  six  ounces  of  the  crystals 


THE  BOOK  OF  THE  LANTERN. 


119 


have  been  so  added,  set  the  basin  aside  for  an  hour  or  two, 
then  stir  its  contents  with  a  glass  rod,  and  test  with  blue 
litmns  paper,  adding  crystals  of  acid  until  the  paper  turns 
slightly  red.  Add  to  the  liquid  30  grains  of  potassic 
bromide,  allow  to  settle,  and  bottle  off  for  use  when  clear. 

But  those  who  wish  to  avoid  the  trouble  of  making 
their  own  potassic  oxalate  can  buy  the  crystals  at  any 
photographic  dealer's,  in  which  case  its  solution  should  be 
made  with  boiling  water,  and  well  stirred  until  all  crystals 
have  disappeared.  One  pound  of  oxalate  will  require 
just  a  quart  of  water  to  make  a  saturated  solution.  If 
more  water  be  used,  the  solution  will  not  be  a  saturated 
one,  and  will,  when  mixed  with  the  iron,  throw  down  a 
muddy  red  precipitate,  and  be  useless  for  developing  pur- 
poses. The  iron  must  be  added  to  the  potash,  and  not  vice 
versa,  or  the  same  effect  will  be  produced.  I  have  found 
that  with  this  developer  it  is  always  advisable  to  soak  the 
exposed  plate  in  water  as  a  preliminary  step.  The  gelatine 
surface  then  takes  more  kindly  to  the  solution,  and  greater 
density  is  attained. 

The  development  should  be  carried  on  until  the  picture 
looks  overdone,  for  it  must  be  remembered  that  it  has  to 
be  ultimately  exhibited  by  transmitted  light,  and  we  view 
it  in  the  developing  dish  by  reflected  light  only,  but  hold- 
ing it  up  to  the  red  light  and  looking  through  it  we  can 
judge  well  when  the  developing  action  ought  to  be  stopped. 
Now  follows  a  rapid  rinse  under  the  tap,  a  few  minutes' 
immersion  in  alum  and  water,  and  fixing  in  fresh  hypo. 
If  ordinary  household  water  has  been  used,  the  film  will 
show  a  milky  veil.    This  is  quickly  removed  by  a  ten  per 


120 


THE  BOOK  OF  THE  LANTERN. 


cent,  solution  of  sodic  citrate,  poured  on  and  off,  and  gently 
rubbed  upon  the  gelatine  surface  with  a  plug  of  cotton 
wool.  This  treatment  is  not  necessary  if  rainwater  is 
available.  Messrs.  Mawson  and  Swan  supply  an  admirable 
plate  for  lantern-slide  work.  It  can  be  used  for  reducing 
in  the  camera,  or  for  contact  printing,  and  is  amenable  to 
more  than  one  method  of  development. 

At  one  of  the  exhibitions  this  firm  showed  a  specimen 
frame  of  four  transparencies  from  one  negative, — each 
developed  by  a  different  formula,  and  showing  a  difference 
of  tint  for  each. 

I  append  two  of  these  formulae  : — 

A.  — Meta  Bisulphite  Developer. 

B.  — Carbonate  Soda  „ 

A. 

I. 

Pyrogallic  Acid    40  grs. 

Meta-bisulphite  Potass    120  „ 

Bromide  Ammonium  ...        ...        ...        ...  40  „ 

Distilled  Water    20  ozs. 

IT. 

Liquor  Ammonia       ...        ...        ...        ...         2^  drms. 

Distilled  Water    20  ozs. 

Mix  equal  parts  of  A  and  B  just  before  using. 

B. 

L  II. 

Pyro  40  grs.       Carb.  Soda   1  oz.  avd. 

Sodic  Sulphite         ...180   „  Sodic  Sulphite     ...  1 

Brom.  Potass  20    ,,         Distilled  Water    ...  20  „  fluid. 

Hydrochloric  Acid    ...  40  mins. 
Distilled  Water  up  to  20  ozs. 

Equal  parts. 

Between  development  and  fixation  immerse  plate  in  Sol.  of  Alum, 
1  oz.  in  20  ozs.  water,  washing  carefully  before  and  after. 


THE  BOOK  OP  THE  LANTERN. 


121 


Messrs.  Samuel  Fry  and  Co.,  also  make  a  thoroughly 
reliable  lantern  plate  which  is  suited  to  both  camera  and 
contact  work.  It  is  amenable  to  more  than  one  developer, 
but  I  prefer  that  in  which  hydrokinone  takes  the  place  of 
pyro.    Here  is  their  formula : — 

A. 

Hydrokinonp,  best  quality         ...*       „#       ...      150  grs. 
Sulphite  Soda       ...        ...        ...       ...       ...     440  „ 

Brom.  Pot.  ...        ...        ...        ...       ..♦       ...       25  „ 

Water — To  make  a  total  bulk  of    20  ozs. 

B. 

Carb.  Soda  (not  Bicarb.)  ...    900  grs. 

Oarb.  Potass         ...       ...   ,       ...     900  „ 

Water — To  make  a  total  bulk  of  ...       ...       20  ozs. 

These  solutions  do  not  require  further  dilution. 

For  Use. — Take  equal  quantities  of  each.  The  mixed  solution 
should  be  colourless,  and  can  be  used  repeatedly,  and  until  the 
developer  fails  to  render  details  satisfactorily. 

LANTERN  SLIDES  FROM  PAPER  PRINTS — ENGRAVINGS  OR 
PHOTOGRAPHS. 

There  are  certain  main  principles  to  be  observed  in 
copying  a  photograph,  or  any  other  kind  of  picture,  if  a 
satisfactory  negative,  fit  for  printing  a  lantern  slide  from, 
is  to  be  expected.  The  copy  should  be  illuminated  by 
diffused  light  only,  and  should  never  receive  the  direct 
rays  of  the  sun.  A  cloudless  day  is  the  best  to  choose, 
for  then  the  light  is  regular,  and  when  the  exposure  has 
been  correctly  calculated  for  the  first  picture,  it  will,  during 
some  hours  of  the  day,  be  right  for  the  rest.  At  least  this 
is  true,  if  we  are  copying  a  series  of  pictures  of  the  same 
dimensions.  But,  if  our  first  copy  is,  say,  12  inches  across 
and  our  next  one  only  carte  de  visite  size — and  we  want  to 
reproduce  a  negative  of  each,  measuring  3J  x  3|  (the 
standard  size  for  lantern  pictures),  our  camera  must  in  the 


122 


THE  BOOK  OF  THE  LANTERN". 


latter  cases  be  so  much  extended  that  the  exposure  must 
be  proportionately  increased. 

A  picture  under  glass  will  seldom  give  a  good  result 
for  the  surface  will  take  up  reflections  from  surround- 
ing objects,  which  may  not  perhaps  be  noticed  on  the 
focussing  screen,  but  which  will  most  surely  become  dis- 
agreeably evident  in  the  negative.  A  highly  glazed 
albumenized  print  is  objectionable  for  the  same  reason, 
but  can  be  generally  coaxed  into  a  position  in  which  no 
mischief  of  the  kind  is  apparent.  Steel  engravings  have  no 
gloss,  but  they  seldom  make  good  pictures  for  the  lantern 
screen,  their  details  being  too  fine.  A  first-class  wood 
engraving  is  far  better  for  the  purpose,  and  as  its  value  is, 
as  a  rule,  not  very  great,  it  can  be  judiciously  touched  up 
before  being  photographed.  Perhaps  the  artist  of  such  a 
picture  would  be  horrified  at  his  work  being  thus  interfered 
with,  but  the  touching  up  indicated  is  quite  legitimate. 
Let  me  further  explain  my  meaning.  Suppose  that  in  one 
of  our  illustrated  periodicals  there  is  a  representation  of 
some  current  event  which  we  want  for  our  lantern.  If  it 
is  an  interior  view,  it  will  probably  require  no  doctoring.  But 
if  a  landscape,  or  a  group  of  figures  with  a  sky  back- 
ground, then  certain  parts  should  be  suppressed.  The  sky 
is  not  white,  but  consists  of  a  number  of  parallel  lines  with 
clouds  interspersed ;  effective  enough  in  the  print,  but  not 
suitable  for  reproduction  in  an  enlarged  form.  These  lines, 
which  seem  to  mingle  so  well,  giving  the  effect  of  a  general 
soft  "  tint/'  will  on  the  lantern  sheet  look  like  what  they 
really  are — a  series  of  detached  bars  right  across  the  picture. 
To  get  rid  of  these  lines,  the  outline  of  the  figures,  and 


THE  BOOK  OF  THE  LANTERN. 


123 


other  objects  which  stand  against  the  sky,  should  have  a 
broad  margin  painted  round  them  in  Chinese  white,  leaving 
the  main  body  of  the  sky  to  be  blocked  out  with  black 
varnish  in  the  negative  itself. 

I  have  done  excellent  work  with  Ross's  portable  sym- 
metrical lens  No.  3 — which  has  a  focus  of  5  inches.  Of 
course,  other  lenses  will  do  well  for  copying,  but  if  of 
longer  focus,  the  camera  must  have  an  extending  front 
fitted  to  it.  Very  few  cameras  pull  out  long  enough  to 
photograph  a  very  near  object,  unless  a  short  focus  lens  is 
employed.  As  a  guide  to  exposure,  I  may  mention  that 
in  copying  wood-cuts  and  photographs  with  the  above- 
named  lens,  and  using  a  fairly-rapid  gelatine  plate,  it 
averages  17  seconds  with  stop  No.  4.  It  is  as  well  to  focus 
with  full  aperture  of  the  lens,  and  to  insert  the  stop  just 
before  exposure.  One  more  hint.  It  is  sometimes  very 
difficult  to  sharply  focus  a  soft  photograph  which  has  no 
sharp  lines  in  itself.  The  difficulty  is  obviated  by  affixing 
to  the  middle  of  the  copy  any  little  piece  of  printed  matter, 
wetting  it  with  the  tongue  for  that  purpose.  Only  be 
careful  to  remove  it  before  exposure,  or  your  negative  will 
faithfully  record  the  little  dodge. 

It  would  seem  a  very  simple  matter,  to  one  who  has  not 
tried  it,  to  fasten  a  picture  upon  a  wall  in  a  good  light, 
stand  the  camera  on  its  tripod  in  front  of  that  picture,  and 
proceed  to  copy  it.  But  difficulties  crop  up  when  we  want 
to  reduce  that  picture  to  a  certain  size,  and  to  keep  the 
camera  square  with  the  copy,  so  as  to  prevent  distortion. 
With  head  beneath  the  focussing  cloth,  the  struggle  to 
adjust  the  tripod  legs  is  quite  distressing.    I  myself  found 


124 


THE  BOOK  OF  THE  LANTERN. 


so  much  difficulty  in  getting  the  camera  into  the  exact 
position  required,  that  I  constructed  a  special  piece  of 
apparatus  for  the  sole  purpose  of  copying.  To  this  acces- 
sory, which  works  most  perfectly,  I  now  direct  atten- 
tion. It  is  simple  in  construction,  and  anybody  who  knows 
how  to  handle  a  few  tools  can  put  it  together  with  ease. 
The  amateur  may  prefer  to  employ  a  professional  carpenter, 
but  there  is  always  a  difficulty  in  getting  the  British  work- 
man to  make  anything  that  is  at  all  strange  to  him.  My 
advice  is,  therefore,  if  you  want  the  thing  done  well  do 
yourself  (see  fig.  40). 


Fig. 


THE  BOOK  OF  THE  LANTERN. 


125 


A  is  a  base  board,  fixed  on  legs,  as  shown.  It  will  be 
evident  that  a  spare  table,  or  even  the  top  of  a  packing- 
case,  wonld  do  as  well,  bnt  it  must  be  firm.  Upon  this  base, 
and  fixed  firmly  to  it,  is  a  kind  of  railway  formed  by  two 
parallel  grooves.  D  is  a  skeleton  carriage  fnrnished  with 
two  rnnners  at  the  bottom  which  will  fit  the  grooves  in 
A,  so  as  to  rnn  easily  to  and  fro.  The  carriage  D  is  also 
furnished  with  grooves,  and  these  are  for  the  reception  of 
the  runners  affixed  to  the  super-carriage,  E.  Upon  E  is 
fastened  the  photographic  camera,  the  camera  screw  being 
placed  through  the  centre  hole  for  that  purpose. 

In  use,  the  picture  to  be  copied  is  pinned  to  the  back- 
board, F,  and  I  may  mention  as  a  detail  of  some  im- 
portance, that  the  little  bead-headed  arrangements  known 
to  drapers  as  "  ladies1  bonnet- pins  "  are  best  for  the  purpose. 
The  camera  is  placed  on  E,  E  on  D,  and  D  placed  on  the 
rails  of  the  baseboard,  A.  We  thus  have  two  separate 
movements  at  our  disposal  in  getting  the  image  of  the  copy 
focussed  centrally  on  the  ground  glass.  A  furnishes  the 
to  and  fro  movement,  and  the  grooves  on  D  give  the  right 
and  left  movement.  The  board,  F,  runs  between  upright 
grooves,  and  thus  we  have  a  vertical  movement.  With 
this  simple  contrivance  a  picture  can  be  focussed  in  a  few 
seconds,  and  the  camera  all  the  time  is  bound  to  keep  square 
with  the  copy.  A  3 -inch  circle  drawn  in  pencil  on  the 
ground-glass  of  the  camera  is  useful  as  a  reminder  of  the 
size  to  which  the  picture  must  be  reduced. 

Lastly,  this  useful  contrivance  can  serve  another  pur- 
pose. We  may  wish  to  obtain  a  reduced  positive  on  glass 
from  a  larger  negative.     We  can  do  this  direct  in  the 


126 


THE  BOOK  OF  THE  LANTERN. 


camera  by  placing  the  negative  to  be  copied  in  an  opening 
in  the  board,  F,  marked  by  a  dotted  line  in  the  illustra- 
tion. A  couple  of  laths  can  then  be  placed  above,  so  as  to 
rest  at  one  end  on  the  camera,  and  at  the  other  end  on  the 
top  of  the  board,  F.    These  laths  will  serve  as  a  support 


Fig.  41. 

for  a  dark  cloth,  which  can  be  thrown  over  all.  A  sloping 
piece  of  white  cardboard  placed  behind  F  (also  indicated 
by  a  dotted  line)  will  throw  reflected  light  from  the  sky 
through  the  negative.  I  give  no  dimensions  for  this  copy- 
ing machine,  for  the  maker  must  be  guided  by  the  size 
of  his  camera,  the  focus  of  his  lens,  and  his  general 
requirements.  A  compound  frame  for  negatives  of  various 
sizes,  as  shown  in  fig.  41,  makes  this  copying-machine 
complete. 


CHAPTER  X. 

HOME-MADE  GELATINE  PLATES. 

LL  makers  of  commercial  gelatine  plates  put  for- 
ward the  quality  of  rapidity  as  being  the  one 
thing  needful  in  modern  photography,  and  ad- 
vertise their  wares  as  being  ten,  twenty,  or  even  sixty 
times  as  quick  in  operation  as  the  old  wet  collodion 
process.  Such  rapid  plates  are  not  the  best  for  trans- 
parency work,  and  as  no  maker  will  acknowledge  that 
his  plates  are  slow, — although  opinions  may  be  divided 
upon  the  matter, — and  as  slow  plates  are  the  most 
suitable  for  lantern  slides,  the  operator  who  aims  at  the 
best  work  may  wish  to  try  his  hand  at  making  them  for 
himself.  Of  the  many  f ormulse  which  I  have  tried  for  this 
particular  purpose,  I  prefer  that  first  introduced  by  Dr. 
Eder,  which  I  have  slightly  modified.  Gelatine  plate 
making  is  by  no  means  easy  work,  but  the  method  which 
I  am  about  to  describe  presents  fewer  difficulties  than 
most  others. 

The  apparatus  required  need  only  be  of  a  very  homely 


128 


THE  BOOK  OP  THE  LANTERN. 


nature,  and  such  as  can  be  found  in  most  households. 
Here  is  the  list : — An  earthenware  pot  with  a  cover  to  it, 
of  about  one  pint  capacity  ;  a  glass  tumbler ;  a  preserving- 
pan  or  saucepan  standing  on  a  tripod,  with  a  spirit-lamp 
or  Bunsen  flame  beneath  it;  a  thermometer,  two  glass 
stirring  rods,  a  square  of  Berlin-work  canvas,  an  earthen- 
ware colander,  and  a  dish.  In  the  earthenware  pot  put 
the  following : — 

Gelatine   110  grains. 

Potassic  Bromide...        ...       ...         62  „ 

(Ten  per  cent.)  Solution  of  Salicylic  Acid  in  Alcohol,     £  ounce. 
Water    2  ounces. 

I  recommend  the  use  of  either  Autotype,  the  Swiss,  or 
Henderson's  make  of  gelatine.  After  being  weighed  it 
should  be  cut  up  into  strips  with  scissors  and  placed  in  the 
jar  with  the  other  ingredients.  With  a  glass  rod  press 
down  the  gelatine  into  the  water y  so  that  every  particle  of 
it  is  wet  and  softened.  Set  aside  for  ten  minutes  to  swell. 
Now  half  fill  the  preserving-pan  with  warm  water,  and 
place  the  flame  beneath  it.  The  thermometer  should  be 
placed  in  the  pan,  so  as  to  check  the  temperature,  which 
should  not  be  allowed  to  rise  about  96°  Fahr.  Place  the 
pot  containing  the  gelatine  in  the  water,  taking  the  precau- 
tion to  put  a  piece  of  thick  paper  beneath  it,  so  that  it 
does  not  actually  touch  the  heated  bottom. 

The  gelatine  will  very  gradually  melt,  and  the#  opera- 
tion may  be  hastened  by  an  occasional  stir  with  the  glass 
rod.  Even  when  it  becomes  quite  limpid,  little  particles 
of  undissolved  gelatine  may  be  floating  about  in  it 
and  these  should  disappear  before  proceeding  further,  or 


THE  BOOK  OF  THE  LANTERN. 


129 


they  will  form  insoluble  particles,  which  will  lead  to 
difficulties  later  on.    In  the  glass  tumbler  place — 

Silver  nitrate  •••  77  grains. 
Water        ...       ...         2  ounces. 

The  common  tap  water  employed  will,  on  account  of  the 
salts  which  it  contains,  turn  milky  in  appearance  when  the 
silver  is  added.  This  is  of  no  consequence.  The  crystals 
can  be  crushed  under  the  water  by  another  glass  rod, 
and  complete  solution  will  soon  be  effected.  (The  tyro 
must  be  most  careful  to  keep  each  stirring  rod  distinct,  or 
he  will  spoil  the  entire  work.)  When  the  crystals  have 
all  disappeared,  pour  into  the  silver  solution,  drop  by  drop, 
some  strong  liquid  ammonia,  stirring  the  solution  vigorously 
all  the  time.  The  liquid  will  turn  coffee-coloured,  owing 
to  a  precipitation  of  silver  oxide,  but  as  more  of  the 
ammonia  is  added  this  precipitate  is  redissolved,  and  the 
solution  becomes  as  clear  as  ordinary  water.  Only  just 
sufficient  ammonia  should  be  added  to  accomplish  this 
result.  Now  place  the  glass  tumbler  in  the  pan  beside 
the  vessel  containing  the  gelatine  mixture,  and  leave  it 
there  to  warm  for  about  fifteen  minutes.  All  the  fore- 
going operations  can  be  conducted  in  the  full  light  of  day, 
but  now,  when  the  two  solutions  have  to  be  blended  to  form 
a  sensitive  emulsion  of  bromide  of  silver,  the  light  of  the 
red  room  only  must  be  called  into  requisition. 

The  flame  beneath  the  pan,  or  water  bath,  is  now  no 
longer  required,  so  let  it  be  removed.  Take  both  the  gela- 
tine and  silver  vessels  from  the  pan,  and  place  them  on  the 
table.    Now  stir  the  gelatine  briskly,  and  add  a  small 

K 


130 


THE  BOOK  OF  THE  LANTERN. 


portion  of  the  silver  solution  at  a  time,  until  all  of  it  is 
transferred  to  the  earthenware  pot.  Wash  out  the  silver 
glass  with  half  an  ounce  of  water  and  add  that  too.  The 
newly-formed  emulsion  should  now  look  like  cream.  Place 
the  cover  on  the  jar,  and  put  it  back  once  more  in  the 
warm  water  (without  any  flame  beneath  it)  for  fifteen 
minutes.  At  the  end  of  that  time  pour  it  out  into  a  dish 
or  plate  to  set,  and  cover  it  over  so  that  neither  light  nor 
dust  can  trouble  it.  This  will  complete  the  first  stage  of 
plate- making. 

In  a  few  hours, — according  to  the  general  temperature, 
— the  emulsion  will  have  set  into  a  firm  jelly.  It  must 
now  be  washed  to  get  rid  of  certain  extraneous  matter 
which  has  been  formed  and  which  is  not  wanted.  The 
silver  nitrate  has  combined  with  the  bromide  of  potassium 
to  form  silver  bromide, — the  required  salt,  which  is  sensi- 
tive to  light,— but  at  the  same  time  nitrate  of  potassium 
(saltpetre)  has  also  been  formed,  and  must  be  eliminated. 
As  this  latter  is  soluble  in  water,  while  the  silver  bromide 
is  insoluble,  the  matter  is  not  a  difficult  one  to  accomplish. 
By  dividing  the  jelly  into  shreds,  and  putting  it  into 
several  changes  of  water,  this  universal  solvent  gets  to 
every  side  of  it,  so  to  speak,  and  the  saltpetre  is  quickly 
got  rid  of.  Scrape  up  the  jelly  with  a  silver  spoon,  or  a 
slip  of  glass,  and  place  it  in  the  middle  of  the  square  of 
canvas,  which  has'  been  previously  wrung  out  in  water. 
Gather  up  the  ends  so  that  the  jelly  forms  a  ball  confined 
within  the  canvas.  Now  place  in  a  large  pan  of  water, 
and  squeeze  and  twist  the  canvas  with  the  hands  (under 
water)  so  that  the  jelly  is  forced  through  the  meshes  of  the 


THE  BOOK  OF  THE  LANTERN. 


131 


fabric  like  so  much  vermicelli.  It  will  presently  sink  to 
the  bottom  of  the  pan.  Wow  pour  off  the  water  above  it, 
and  fill  up  with  fresh.  Let  the  pan  rest  for  five  minutes, 
and  repeat  the  operation  half  a  dozen  times.  The  emulsion 
must  now  be  strained. 

A  square  of  cambric,  the  size  of  a  handkerchief,  is 
squeezed  in  water,  and  put  in  the  colander,  so  as  to  form  a 
lining  to  it,  with  the  corners  hanging  outside.  Pour  the 
divided  emulsion  into  this,  when  most  of  the  water  will 
at  once  run  off,  and  still  more  may  be  made  to  do  so  by 
gathering  up  the  corners  of  the  cambric  in  the  hands  and 
gently  squeezing  the  pudding-like  mass.  Once  more  open 
the  cloth,  and  pour  into  the  contained  emulsion  an  ounce 
of  methylated  spirit.  Again  squeeze  up  the  cloth,  after 
which  the  gelatine  shreds  can  be  spooned  up,  placed  in  a 
clean  jar,  and  tied  over  with  a  light-tight  cover.  So  ends 
stage  number  two. 

There  are  many  who  say,  with  much  truth,  that  the  real 
difficulty  of  plate-making  begins  after  the  foregoing  opera- 
tion of  making  the  emulsion,  for  a  great  many  fail  in  the 
mechanical  work  of  coating  the  plates,  which  is  the  next 
and  final  operation.  Before  this  is  attempted  the  decks 
should  be  cleared  for  action.  The  operator  must  have  on 
his  table  a  carefully  levelled  piece  of  slate  or  plate  glass, 
large  enough  to  contain  at  least  one  dozen  plates,  laid 
edge  to  edge.  He  will  also  want  a  jug  with  a  good  lip 
from  which  to  pour  the  emulsion,  a  glass  rod  to  guide 
it  over  the  plate  which  he  is  coating,  and  a  pneumatic 
holder.  The  jar  of  emulsion  must  first  of  all  be  placed  in 
the  water  bath  at  the  old  temperature  of  96°  for  an  hour 

K  2 


132 


THE  BOOK  OF  THE  LANTERN. 


or  two,  during  which  time  it  can  be  conveniently  stirred 
once  or  twice  (by  red  light  only,  of  course).  If  the  cover 
of  the  jar  be  really  light  tight,  this  melting  operation  can 
go  on  in  daylight,  and  at  the  same  time  the  glass  to  be 
coated  can  be  cleaned.  Polish  each  glass  with  a  little 
whiting  and  water,  and  when  dry  rub  the  side  to  be 
coated  with  a  leather  damped  with  spirits  of  wine.  This 
will  counteract  any  repellant  action  when  the  emulsion  is 
applied  to  the  glass  surface.  When  all  the  glasses  have 
been  so  treated,  wrap  them  in  packets  of  two  dozen  each, 
in  clean  paper,  prepared  side  upwards,  and  put  them  on 
the  kitchen  hob  to  warm  through.  (This  latter  precaution 
is  only  necessary  in  cold  weather.)  The  emulsion  must 
now  be  filtered. 

The  best  form  of  filter  is  a  lamp  chimney  with  a  flange 
on  its  lower  orifice,  over  which  a  piece  of  damp  wash- 
leather  (which  has  been  washed  in  soda  and  rinsed  in 
many  changes  of  water)  can  be  tied.  When  all  is  ready 
for  commencing  to  coat,  this  filter  is  held  over  the  mouth 
of  the  jug  (both  should  be  rinsed  out  with  warm  water 
the  instant  before),  and  the  emulsion  is  poured  steadily  into 
its  upper  opening.  In  a  minute  it  will  run  through  the 
leather  into  the  jug  below,  and  will  be  quicker  in  its  move- 
ment if  a  pressure  of  air  is  kept  upon  it,  by  applying  the 
lips  to  the  upper  end  of  the  glass.  Now  comes  the  coating 
difficulty. 

Let  the  operator  seat  himself  at  his  table  so  that  the 
slate  or  glass  slab  is  between  him  and  the  red  light. 
Place  the  glass  rod  in  the  jug  of  emulsion,  and  when  in 
the  act  of  pouring  keep  the  rod  back  with  the  thumb  of 
the  same  hand  that  is  holdingthe  jug.    Take  the  topmost 


THE  BOOK  OF  THE  LANTERN. 


133 


glass  plate,  fix  it  on  the  pneumatic  holder,  hold  it  level, 
and  pour  a  small  pool  of  emulsion  in  its  centre.  By  inclin- 
ing the  plate  a  little,  the  pool  will  run  to  the  two  further 
corners,  and  can  afterwards  be  guided  across  the  whole 
plate  with  the  help  of  the  glass  rod.  The  plate  is  then 
slid  on  to  the  slab,  where  it  will  speedily  set,  and  the  glass 
rod  goes  back  into  the  jug.  Each  plate  is  treated  in  the 
same  way  until  the  slab  is  full,  by  which  time  its  first 
occupants  will  have  set,  and  can  be  reared  up  to  dry  in 
shelves,  or  a  proper  drying  cupboard.  The  glass  chosen 
should  be  as  thin  and  as  free  from  bubbles  as  possible,  and 
can  be  of  the  standard  lantern  size,  3^  by  3^  inches.  But 
as  experience  is  gained  the  operator  will  find  it  more  con- 
venient and  economical  of  time  to  coat  plates  6|  by  6^  inches, 
which  can  afterwards  be  cut  across  twice  with  the  dia- 
mond, to  form  each  four  lantern  slides. 


GELATINO-CHLOKIDE  PLATES. 

My  own  favourite  process  for  lantern  slide  making  is  the 
gelatino-chloride,  which  has  many  good  points  to  recom- 
mend it.  It  is  suitable  only  for  contact  printing,  there- 
fore the  negatives  used  must  be  small  ones  only.  Capital 
chloride  plates  can  be  purchased  nowadays  ;  but  for  those 
who  prefer  to  make  their  own,  I  can  confidently  recom- 
mend the  following  formula  :  Mix  up  the  three  solutions 
— A,  B,  and  0. 


(  Gelatine 
(  Water  (distilled) 
Silver  Nitrate 
Water  (distilled) 
(  Ammonium  Chloride' 
I  Water  (distilled) 


300  grains. 

4  ounces. 
240  grains. 

4  ounces. 
100  grains. 

2  ounces. 


134 


THE  BOOK  OF  THE  LANTERN. 


Melt  by  heat,  but  not  above  120°  Fahr.  Then  in  a 
yellow  light,  ponr  B  into  A,  stirring  rapidly  all  the  time, 
and  finally  adding  0.  Allow  the  emulsion  thua  made  to 
remain  for  one  hour,  at  the  temperature  already  stated, 
and  then  put  aside  in  a  dish  to  set.  The  washing,  filtering, 
and  coating  operations  are  the  same  as  those  described  for 
bromide  plate  making.  The  bright  yellow  light  allowable 
is  a  great  help  to  comfortable  working  of  this  process. 

Chloride  plates  are  useless,  on  account  of  their  slowness, 
where  a  slide  has  to  be  reduced,  by  means  of  the  camera, 
from  a  negative  larger  than  itself.  Nor  do  I  advise  the 
amateur  to  adopt  them  unless  he  can  work  by  daylight, 
or  is  fortunately  situated  like  one  I  know,  who  lives  oppo- 
site to  an  enterprising  tailor  who  displays  an  electric  arc 
light  in  front  of  his  door.  For  the  chloride  plate  is  most 
insensitive  to  yellow  light,  such  as  that  afforded  by  gas. 
For  this  reason,  most  commercial  makers  advise  that  the 
light  chosen  should  be  that  procured  by  burning  an  inch  of 
magnesium  wire  at  a  distance  of  so  many  inches  from  the 
printing-frame.  This  advice  is  not  difficult  to  follow,  but 
it  is  very  difficult  to  make  two  pieces  of  wire  give  out 
exactly  the  same  amount  of  light ;  for  magnesium  wire  has 
a  habit  of  dropping  down  in  a  languid  manner  under  the 
influence  of  its  own  heat,  and  going  out  suddenly  when  it 
ought  to  shed  its  radiance  abroad.  With  diffused  daylight 
all  is  plain  sailing.  The  negative,  with  its  chloride  plate 
in  contact  with  it,  is  exposed,  say,  for  three  seconds  to 
daylight,  and  is  then  dropped  into  the  developer.  Here 
is  a  good  one,  devised,  if  I  remember  rightly,  by 
Mr.  Edwards : — 


THE  BOOK  OF  THE  LANTERN. 


135 


C  Neutral  potassic  oxalate    2  ounces. 

A  <  Sal  ammoniao         ...        ...        ...    40  grains. 

t  Water  (distilled)    1  pint. 

f  Iron  sulphate         ...        ...       ...  4  diaohms. 

•p  \  Citric  acid    ...        ...        ...        ...  2 

15  1  Alum   2 

(.  Water  (distilled)    1  pint. 

For  use,  pour  a  portion  of  B  into  an  equal  quantity  of  A. 

If  the  operator  is  accustomed  to  the  ferrous  oxalate 
developer  pure  and  simple,  he  will  find  that  it  will  develop 
this  description  of  plate,  but  it  is  better  for  being  restrained 
with  a  few  drops  of  10  per  cent,  solution  of  sodic  citrate. 
Whether  he  use  one  or  the  other,  let  him  be  particularly 
careful  in  the  matter  of  cleanliness  of  fingers.  A  hypo- 
defiled  finger  will  spoil  the  developer  instantly.  To  avoid 
this  disaster, — the  potency  of  which  I  have  learned  by 
sad  experience, — I  have  adopted  the  following  method  of 
working : — 

I  use  a  brilliant  yellow  light,  so  that  I  can  work  comfort- 
ably, for  chloride  plates  are,  as  already  stated,  insensitive  to 
yellow  rays ;  the  developing  tray  stands  in  front  of  it,  and  at 
one  side  is  placed  a  large  tray  filled  with  water,  to  which  a 
little  alum  solution  has  been  added.  Hypo  is,  for  the  pre- 
sent banished  from  the  scene  altogether.  I  expose  my  plate, 
and  put  it  into  the  developing  solution.  In  a  few  seconds 
the  picture  flashes  out  in  the  unceremonious  manner  com- 
mon to  chloride  plates.  I  hold  it  up  to  the  light,  look 
through  it,  and  find  that  it  is  but  a  ghostly  image  after  all. 
I  expose  another  plate  in  an  adjoining  room,  and  put  it  by 
the  one  which  is  in  course  of  development,  and  which  by 
this  time  has  most  likely  gained  sufficient  density.  If  it 
has,  I  wash  it  for  a  few  seconds  under  the  tap,  and  drop  it 


136 


THE  BOOK  OF  THE  LANTERN. 


into  the  alum  tray  ;  and  so  on,  until  perhaps  a  couple  of 
dozen  plates  have  been  treated  in  the  same  way.  I  then 
light  my  gas-lamp,  mix  up  a  tray  of  fresh  hypo,  large 
enough  to  accommodate  half  a  dozen  plates  at  a  time,  and 
proceed  to  fix  my  plates.  They  fix  rapidly,  and  as  fast  as 
they  are  done,  back  they  go  into  the  weak  alum  solution, 
until,  when  the  batch  is  finished,  I  proceed  to  wash  them. 
This  I  do  by  placing  them  in  a  metal  rack  (see  fig.  42), 
and  changing  the  water  occasionally  during  an  hour  or  so. 


Fig.  42. 


GENERAL  CONSIDERATIONS — INTENSIFYING  AND  MOUNTING. 

Hitherto  I  have  said  nothing  with  reference  to  the  best 
kind  of  negative  for  lantern  slide  making  ;  the  worker  will 
find  out,  after  a  few  trials,  that  some  of  his  negatives  will 
yield,  without  much  trouble,  a  first-class  result,  whilst  others 


THE  BOOK  OF  THE  LANTERN. 


137 


seem  reluctant  to  give  anything  but  a  very  poor  trans- 
parency. A  really  good  negative  will  give  a  good  print 
on  paper,  glass,  or  indeed  on  any  other  possible  material, 
but  at  the  same  time  a  negative,  which  from  its  thinness 
would  require  special  management  in  ordinary  printing  on 
albumenised  paper,  will  yield  a  fine  transparency  on  glass 
with  half  the  trouble.  In  other  words,  a  negative  taken 
purposely  for  lantern  work  need  not  be  so  dense  as  one 
destined  for  the  ordinary  printing-frame.  The  precautions 
used  in  dealing  with  a  thin  negative  in  the  one  case,  must 
be  observed  in  the  other ;  for  instance,  the  careful  printer, 
in  producing  a  paper  print  from  such  a  negative,  will  take 
his  frame  far  from  the  window  of  his  room,  and  give  it  a 
very  protracted  exposure,  and,  by  coaxing  it  in  this  way,  a 
good  dense  print  is  obtainable.  Exactly  the  same  treat- 
ment is  necessary  in  producing  a  lantern-slide  from  the 
same  picture.  Instead  of  holding  the  printing-frame  a  foot 
or  two  from  the  gas-burner,  as  already  recommended,  let  it 
be  removed  6  feet  away  from  the  flame,  and  be  given  a 
greatly-increased  exposure  by  the  rule  already  indicated. 

I  have  advised  that  the  focussing-screen  of  the  camera 
should  be  marked  with  a  3-inch  circle,  to  which  the 
picture  should  be  limited.  A  still  more  effective  plan, 
however,  is  to  cover  the  ground-glass  with  a  card- 
board mask,  having  a  3 -inch  hole  in  its  centre,  which 
can  be  placed  in  situ  when  required.  The  operator  can 
then  see  at  a  glance  whether  his  pictare  is  nicely  composed, 
and  will  have  a  very  good  idea  of  its  ultimate  appearance 
as  a  lantern-slide  on  the  sheet.  Most  photographers  carry 
into  the  field  with  them  more  than  one  lens,  and  it  is  espe- 


138 


THE  BOOK  OF  THE  LANTERN. 


cially  necessary  that  lie  whose  negatives  are  intended  to 
yield  lantern-pictures  of  a  uniform  size  should  do  so.  The 
beginner  is,  perhaps,  not  likely  to  see  the  advantage  of  this. 
Let  me  point  it  out.  Suppose  that  he  has  focussed  the 
image  of  some  wayside  cottage,  and  finds  to  his  chagrin 
that  the  building  fills  up  all  the  proscribed  circle,  and  that 
the  surrounding  foliage  and  other  accessories  which  really 
make  up  the  beauty  of  the  scene,  as  presented  to  the  eye, 
are  "far,  far  away."  His  natural  impulse  would  be  to 
carry  his  camera  farther  from  the  object,  but  a  blank  wall 
behind  him  forbids  him  to  do  this.  But  with  a  shorter 
focus -lens,  which  should  screw  into  the  flange  fitted  on  his 
camera,  the  accident  can  be  immediately  remedied,  and 
he  can  proceed  on  his  way  rejoicing.  This  same  difficulty 
has  occurred  to  me  time  after  time,  in  the  case  of 
country  churches  having  small  burial-grounds  shut  in  on 
every  side  by  foliage.  From  no  point  can  a  view  of  the 
building  be  focussed  on  the  glass  except  by  using  a  lens  of 
very  short  focus.  Very  often  the  conditions  are  reversed, 
and  the  photographer  finds  himself  before  a  scene  with  some 
obstacle  in  front  of  him  which  forbids  nearer  approach, 
and  the  image  on  the  focussing- screen  is  quite  insignificant. 
Here  the  obvious  course  is  to  screw  off  the  front  lens  of  his 
combination,  and  to  treat  the  back  one  as  a  long-focus 
single  lens.  Of  course,  the  camera  must  be  extended  to 
double  its  normal  length,  and  no  amateur  should  possess  a 
camera  that  will  not  do  so,  should  occasion  require  it. 

The  most  experienced  workers  often  obtain  a  negative 
full  of  brilliancy  and  delicate  detail,  but  with  a  very  thin 
sky, — a  sky  so  thin  that  if  a  lantern-slide  were  taken  from 
it  raw,  so  to  speak,  we  should  have  in  it  a  very  good  repre- 


THE  BOOK  OF  THE  LANTERN. 


139 


sentation  of  a  November  fog.  There  are  several  ways  of 
obviating  this  difficulty.  In  exposing  it  before  the  gas- 
flame  it  should,  like  all  thin  negatives,  be  taken  several 
feet  distant,  so  that  the  time  of  exposure  may  perhaps 
extend  to  twenty  seconds  or  more.  During  this  time  keep 
the  sky  portion  covered  with  a  piece  of  card  which  has 
been  cut  in  Vandykes  all  along  the  edge  next  the  horizon, 
but  do  not  keep  it  still,  but  in  gentle  movement.  This 
plan  gives  a  clear  sky,  with  the  effect  of  a  slight  haze  over 
the  horizon, — an  effect,  I  need  hardly  say,  frequently  seen 
in  nature.  Indeed,  this  hazy  effect  can  often  be  extended 
to  the  landscape  itself,  with  the  most  charming  effect  of 
atmosphere  which  an  artist  could  desire. 

Another  plan  of  treating  a  thin  sky  is  to  furnish  it  with 
clouds  by  the  following  simple  method : — Paste  over  the 
glass  side  of  the  negative  a  piece  of  white  tissue  paper. 
When  this  is  dry,  hold  it  up  to  the  light,  and  mark  upon  it 
the  position  of  the  horizon  and  the  outline  of  any  trees  or 
other  objects  which  may  appear  against  the  sky.  Now, 
with  a  stump  and  a  black  pigment  (such  a  pigment  for  use 
with  the  stump  is  sold  by  most  artists'  colourmen, — I  do 
not  know  the  name)  rub  in  masses  of  cloud,  taking  care 
that  their  edges  are  ill-defined  and  fleecy.  By  this  means 
a  flat,  tame -looking  negative  can  be  made  to  yield  a  beau- 
tiful picture.  Any  water  in  the  composition  can  be  treated 
in  the  same  way,  for  it  must  be  remembered  that  water 
reflects  clouds  as  well  as  anything  else.  Where  the  sky  is 
dense  enough,  but  contains  pin-holes  or  other  blemishes, 
Bates's  black  varnish,  painted  on  the  plain  glass  side,  is  the 
best  remedy ;  or  the  faults  can  be  delicately  stopped  out 
by  ordinary  India  ink  on  the  film  side.    Where  there  is  a 


140 


THE  BOOK  OF  THE  LANTERN. 


large  expanse  of  sky,  the  quickest  method  is  to  gum  over 
it  a  piece  of  orange-coloured  paper  with  a  jagged  edge. 

A  lantern  slide,  otherwise  perfect,  will  sometimes  re- 
quire a  little  strengthening.  I  believe  that  the  best 
method  of  intensification  is  that  long  ago  published  by 
Mr.  England.    Here  it  is  : — 

Mercuric  bi-chloride  (corrosive  sublimate)  ...       \  oz. 
Sal  ammoniac    ...        ....       ...        ...        ...       \  „ 

Water    12  „ 

(Dissolve,  and  mark  "  Poison.") 

The  picture,  after  well  soaking  in  plain  water,  is  im- 
mersed in  this  mixture,  in  which  it  will  first  turn  grey, 
and  afterwards  quite  white  if  left  long  enough.  The 
white  stage  should  not  be  reached  unless  a  very  great 
additional  intensity  is  requisite.  Remove  from  the  solu- 
tion, wash  most  thoroughly  under  a  tap  for  three  or  four 
minutes,  and  immerse  in  the  following  solution,  which  will 
almost  immediately  turn  the  film  to  a  brown  black : — 

Liq.  ammonia-fort       ...        ...        ...        ...       \  drachm. 

Water     ...       ...       ...       ...       ...       ...       6  ounces. 

Rinse  under  the  tap,  and  the  operation  is  complete.  Many 
people  object  to  the  use  of  the  mercuric  salt,  on  the 
ground  that  it  is  unstable,  and  that  the  picture  will  ulti- 
mately fade.  I  have  not  found  this  to  be  the  case  if  the 
washing  operation  be  thoroughly  carried  out,  but  as  a  rule 
I  should  give  an  intensified  film  a  protecting  layer  of 
varnish.  Prevention  is  better  than  cure,  and  the  amateur 
should  endeavour  to  produce  pictures  that  will  require  no 
doctoring. 

When  the  lantern  transparency  is  complete  it  must  be 
mounted  before  it  can  be  considered  out  of  hand.    It  is  as 


THE  BOOK  OF  THE  LANTERN. 


141 


well  to  try  it  in  the  lantern  first,  in  order  that  any  little 
blemish  not  before  detected  can  be  remedied.  Any  little 
clear  spot  where  a  clear  spot  has  no  business  to  be  can  be 
touched  with  India  ink.  If  the  picture  is  to  be  coloured, 
the  slide  need  not  be  so  firmly  bound  up  as  one  to  be  used 
plain.  A  cover  glass,  separated  from  the  photograph  by  a 
paper  mask,  with  a  round,  square,  or  cushion-shaped  open- 
ing, and  fastened  with  one  or  two  slips  of  gummed  (stamp) 
paper,  is  quite  sufficient  until  the  artist  is  ready  with  his 
palette  and  brushes.  But  if  the  slide  is  to  be  exhibited  as 
a  plain  photograph,  it  may  as  well  be  bound  together  as  it 
is  to  remain.  For  this  purpose  we  require  slips  of  gummed 
paper  fourteen  inches  long  by  three-eighths  of  an  inch 
broad.  The  paper  (black  needle  paper  is  the  best)  should 
be  gummed  before  being  cut,  and  one  sheet  will  provide 
for  about  a  hundred  pictures.  Mix  powdered  gum  arabic 
with  one  fourth  its  weight  of  loaf  sugar,  and  add  sufficient 
water  to  make  a  thick  mucilage.  Paint  the  paper  liberally 
with  this,  and  hang  it  up  to  dry.  When  dry  it  can  be  cut 
into  slips  of  the  above  size. 

To  mount  a  picture,  damp  one  of  the  slips  of  gummed 
paper,  and  put  it  sticky  side  upwards  on  the  table  before 
you.  Now  take  a  slide,  duly  fitted  with  its  black  mask,  and 
a  cover  glass,  all  perfectly  clean  and  free  from  dust.  Hold 
the  combination  tightly  between  the  fingers,  and  bring  one 
edge  down  on  the  end  of  the  gummed  slip.  Now  treat  the 
slide  as  a  porter  treats  a  heavy  box, — turn  it  over  and  over 
along  the  slip  of  gummed  paper,  so  that  each  edge  will 
take  up  its  quantum.  Now  carefully  fold  down  the  edges, 
neatly  adjust  the  corners,  and  the  thing  is  done. 


142 


THE  BOOK  OF  THE  LANTEE.N. 


The  black  masks  can  be  bought  ready  cut  at  about  three- 
pence the  dozen,  or  the  worker  can  cut  his  own  if  he  prefer 
it.  Zinc  patterns  are  sold  for  this  purpose,  together  with  a 
clever  cutting  tool,  which  consists  of  a  little  steel  wheel  set 
in  a  handle  (see  fig.  43).    The  pattern  is  placed  above  the 


Fig.  43. 


paper  to  be  cut,  the  little  wheel  is  run  round  the  opening 
in  the  zinc,  and  a  cleanly  cut  mask  is  the  result.  A  sheet 
of  glass  is  the  best  bed  upon  which  to  lay  the  paper  when 
cutting  it.  The  gummed  slips  can  also  be  bought,  but 
those  who  prefer  to  be  self-dependent  will  make  their  own 
in  the  way  described. 

Not  long  ago  I  compared  one  of  my  slides  with  a  wet 
plate — one  taken  from  the  same  negative — by  a  first-rate 
operator,  who  is  used  to  this  class  of  work,  and  hardly 
does  anything  else.  He  was  bound  to  admit  that  the 
gelatine  picture  was  the  better  of  the  two,  and  said  that  he 
should  think  of  relinquishing  his  bath  after  seeing  what 
gelatine  plates  could  do.  I  advised  him  to  do  no  such 
thing.  A  wet  plate  is  so  certain  in  its  results,  that  an 
unskilled  hand,  if  he  be  furnished  with  the  materials,  can 
produce  picture  after  picture  without  difficulty.  I  cannot 
say  the  same  of  gelatine  plates,  for  they  are  such  ticklish 
things  that  oftentimes  something  or  other  will  go  wrong. 


THE  BOOK  OF  THE  LANTERN. 


143 


But  for  the  amateur  worker,  to  whom  a  few  failures  are 
not  of  any  great  moment,  gelatine  plates  are  best  adapted. 
The  silver  bath,  with  its  concomitant  stained  fingers  and 
spoiled  linen,  is,  I  think,  best  left  alone,  unless  the  ama- 
teur adopts  it  as  a  necessary  part  of  his  photographic 
education. 

Those  amateur  photographers  who  are  used  to  the  work- 
ing of  bromide  paper,  can  produce  lantern  slides  by  an 
easier  method  than  any  of  those  just  reviewed,  namely,  by 
means  of  the  transferro-type  paper  which  has  lately  been 
introduced  by  the  Eastman  Company,  and  with  which 
many  succeed  in  producing  very  fine  lantern  slides.  This 
paper  is  coated  with  identically  the  same  emulsion  as  that 
employed  in  the  well-known  bromide  paper,  and  therefore 
the  amateur  has  an  advantage  at  the  outset,  of  working 
with  a  medium  to  which  he  is  accustomed ;  its  develop- 
ment being  the  same  as  that  of  the  ordinary  bromide  paper. 
It  consists  of  an  insoluble  sensitised  emulsion  which  is 
applied  to  paper  having  a  soluble  substratum  of  gelatine. 
The  tissue  is  exposed  under  a  negative  to  gaslight  for 
the  requisite  time,  and  according  to  the  density  and 
other  peculiarities  of  the  negative  in  question ;  and  is  then 
developed  in  a  ferrous-oxalate  solution  in  the  ordinary 
manner.  It  is  then  transferred  to  a  piece  of  plain  glass, 
which  should  be  free  from  bubbles  and  other  blemishes, 
while  wet,  being  placed  face  down  on  the  glass,  and 
squeezed  into  contact.  As  much  moisture  as  possible  is 
then  removed  by  the  application  of  blotting  paper.  In 
about  half  an  hour  it  will  be  ready  for  stripping ;  but  may 


144 


THE  BOOK  OF  THE  LANTERN. 


be  left  if  preferred  until  the  tissue  is  quite  dry.  The  glass 
and  its  print  is  placed  in  a  dish  containing  water  at 
the  temperature  of  about  110  degrees  if  the  print  is  wet; 
but  should  the  print  have  been  allowed  to  dry,  the  water 
must  be  some  1 0  degrees  hotter.  After  allowing  it  to  soak 
for  a  couple  of  minutes  or  so,  the  paper  is  raised  at  one 
corner,  taking  every  precaution  not  to  injure  the  sur- 
face ;  when  it  will  readily  separate  from  the  film.  The 
plate  bearing  the  picture  is  then  put  into  a  solution  of  alum 
for  a  minute,  and  is  placed  in  a  rack  to  dry.  Upon  ex- 
amining a  lantern  slide  so  made,  a  slight  granular  appear- 
ance is  observable  in  the  high  lights  and  the  sky ;  but  this 
is  not  apparent  when  the  image  is  projected  on  the  lantern 
screen.  The  picture  will  have  the  usual  grey  tone,  which 
is  associated  with  ferrous-oxak  te  development ;  but  it  can 
be  turned  to  a  rich  brown  by  the  following  treatment : — 

,  (  Potassium  ferricyanide  ...        ...        ...  100  grs. 

( Water   24  ozs. 

-o  ("Uranium  nitrate  ...   100  grs. 

15  (Water    !   24  ozs. 

Take  equal  parts  of  A  and  B  and  immerse  the  print  in 
the  mixture  until  the  tone  changes  to  the  tint  required. 
Then  wash  thoroughly  and  immerse  for  five  minutes  in  a 
freshly  made-up  solution — hypo,  three  ounces  ;  water,  six- 
teen ounces,  wash.  The  prints  that  will  best  yield  to  this 
after-treatment  are  those  in  which  the  image  is  from  any 
cause  rather  weak ;  for  this  final  bath  not  only  alters  the 
tone,  but  acts  as  an  intensifier. 


CHAPTER  XI. 


ON   COLOURING    PHOTOGRAPHIC    TRANSPARENCIES    FOR  LANTERN 

SLIDES. 


N  giving  directions  for  colouring  lantern  trans- 
parencies, I  am  quite  aware  that  many  persons 
will  say  at  the  outset  that  a  good  photograph  is 
better  without  any  colour  at  all ;  on  the  principle,  I  suppose, 
that  "  good  wine  needs  no  bush." 

I  quite  agree  with  that  opinion,  and  in  colouring  a  trans- 
parency of  good  quality,  I  should  be  inclined  to  describe 
the  operation  more  as  tinting  ;  for  the  common  method  of 
colouring  by  which  photographs  are  blotted  out  and 
drowned  in  a  mass  of  pigment  is  simply  atrocious.  I 
lately  saw  a  photographic  transparency  for  a  lantern,  which 
was  very  beautifully  and  tastefully  tinted,  evidently  by  an 
artistic  hand. 

The  owner  of  this  picture  saw  no  beauty  in  it,  but  com- 
plained to  me  that  he  paid  a  long  price  for  this  thing,  and 
there  was  hardly  any  colour  on  it,  just  as  if  payment  ought 
to  go  by  the  amount  of  pigment  stuck  on  the  glass. 


146 


THE  BOOK  OF  THE  LANTERN. 


In  the  first  place,  the  worker  must  consider  which  of 
his  pictures  will  be  benefited  by  a  coating  of  colour, 
for  some  subjects  are  very  much  better  le£t  alone, 
and  shown  as  untouched  photographs.  This  is  especially 
true  of  such  pictures  as  exhibit  a  mass  of  detail  entirely 
covering  the  glass ;  a  woodland  scene,  for  instance,  with 
tangled  masses  of  branches  and  underwood,  and  ferns  in 
profusion.  On  the  other  hand,  if  the  subject  be  an  open 
landscape,  with  more  than  half  of  it  consisting  of  white 
sky,  it  is  undoubtedly  improved  by  being  tinted.  The 
white  sky  receives,  with  great  benefit,  its  n&fcural  tint  of 
blue,  relieved  by  masses  or  feathery  tufts  of  clouds, 
which,  if  carefully  introduced,  can  be  made  to  look  very 
like  the  real  thing. 

In  the  directions  that  I  am  now  about  to  give,  it  may 
therefore  be  taken  for  granted  that  all  colour  is  to  be  put 
on  most  sparingly,  and  that  its  amount  must  not  be  suffi- 
cient to  obliterate  the  least  detail  in  the  photograph.  Of 
course,  if  a  bad  photograph  is  to  be  coloured  instead  of 
being  thrown  into  the  dust-hole, — which  latter  is  by  far  the 
better  course, — colour  can  be  piled  on  to  it  to  hide  its 
inherent  defects,  but  this  is  only  justifiable  when  the  colour- 
ing is  a  necessity,  and  there  is  no  time  to  procure  a  better 
photograph. 

Let  it  be  understood  that  this  work  of  colouring  lantern 
transparencies  is  not  easy.  It  not  only  requires  a  steady 
hand  and  good  eyesight,  but  it  wants  artistic  perception 
aiso, — at  least,  to  do  it  well.  I  do  not  say  that  a  knowledge 
of  drawing  and  painting  is  absolutely  necessary  to  the  slide- 
painter  ;  but  it  is  certain  that  he  who  understands  the  use 


THE  BOOK  OP  THE  LANTERN. 


147 


of  any  kind  of  colours,  and  has  some  knowledge  of  the  way 
in  which  they  can  be  combined  to  form  different  tints,  will 
paint  a  slide  very  much  better  than  one  who  is  without 
that  knowledge.  Should  he  be  quite  unused  to  working  in 
colour,  he  had  best  begin  by  procuring  some  book  upon  the 
general  theory  of  colouring,  so  that  he  may  understand  the 
difference  between  a  primary,  secondary,  and  tertiary  tint, 
and  may  learn  how  to  combine  them  together.  There  are 
plenty  of  such  books  to  be  had,  and  very  often  the  infor- 
mation is  comprised  in  some  of  those  useful  little  manuals 
on  water-colour  painting  which  can  be  had  of  most  artists' 
colour  men.  I  say  water-colour  painting  advisedly,  for  the 
art  of  slide -painting  partakes  more  of  that  kind  of  art  than 
any  other  ;  for  the  reason  that  it  deals  with  transparent  pig- 
ments. But  do  not  let  it  be  imagined  that  I  recommend 
water  colours  for  the  work  in  hand.  I  know  that  some 
writers  have  advised  their  use,  and  there  is  more  than  one 
manual  which  describes  how  slides  can  be  painted  in  water 
colours.  The  process  may  possibly  have  answered  under 
the  old  conditions,  when  the  majority  of  lantern  slides  were 
made  by  the  wet  process,  and  when  the  artist  had  a  layer  of 
collodion  to  paint  upon.  But  most  of  my  readers  will  wish 
to  colour  their  own  productions  ;  and  as  these  will  probably 
consist  of  gelatine  pictures,  which  any  application  of  water 
will  blister,  I  will  at  once  reject  that  method  of  painting  as 
being  inadmissible. 

First,  I  will  make  a  few  remarks  with  regard  to  the 
apparatus  required,  which  is  of  the  simplest  description. 
A  retouching  desk  will  make  a  good  easel  (see  fig.  44),  or, 
failing  this,  one  can  readily  be  made  by  using  a  sheet  of  glass 

L  2 


148 


THE  BOOK  OF  THE  LANTERN. 


in#a  frame.  A  small  school  slate  measuring  about  8  by  5, 
with  the  slate  knocked  out,  and  a  piece  of  window-glass  put  in 


Fig  44. 


its  place,  makes  a  very  good  easel  for  slide-painting.  This 
should  be  hinged  on  to  a  base  board  with  a  strut  at  one 
side,  so  as  to  keep  it  at  a  convenient  slope  for  working.  A 
sheet  of  white  paper  placed  on  the  base  board  at  the  back 
completes  the  arrangement. 

Beyond  the  easel  we  shall  require  a  palette,  and  a  white 
tile  answers  the  purpose  as  well  as  anything  else  ;  some 
brushes,  a  few  colours,  a  sheet  or  two  of  white  tissue  paper, 
and  a  piece  of  linen  cloth  upon  which  to  wipe  the  brushes. 
One  or  two  bottles  containing  different  media  will  complete 
the  list.  The  colours  employed  are  those  used  by  artists 
for  oil  painting,  and  which  are  enclosed  in  collapsible  metal 
tubes.  But,  unlike  the  oil  painter,  the  lantern-slide  artist 
is  confined  to  the  use  of  those  colours  only  which  are 
naturally  transparent.    To  make  this  clear,  let  us  suppose 


THE  BOOK  OF  THE  LANTERN. 


14!) 


that  any  one  ignorant  of  the  subject  were  to  attempt 
to  use  snch  a  colour  as  vermilion,  which  is  opaque  ;  it 
would  appear  to  be  of  the  usual  vivid  scarlet  when  seen  on 
the  glass,  but  seen  through  the  glass,  it  would  simply  be  a 
black  patch,  because  the  light  cannot  filter  through  it. 
This  being  the  case  with  all  the  opaque  colours,  we  there- 
fore discard  them.  I  now  annex  a  list  of  colours  which  are 
at  the  disposal  of  the  slide -painter,  and  which  are  all  more  or 
less  transparent.  They  are  not  all  actually  essential,  but 
still  the  artist  will  do  well  to  procure  them,  as  they  will 
give  him  an  immense  variety  of  tints  : — 

Prussian  Blue  Brown  Madder 

Indigo  Rose  Madder 

Italian  Pink  Purple  Madder 

Raw  Sienna  Crimson  Lake 

Yellow  Lake  Ivory  Black 

Chinese  Orange  Burnt  Sienna 

Neutral  Tint  McGilp. 
Brown  Pink 

It  will  be  noticed  that  there  is  only  one  brilliant  blue  in 
this  list,  that  is  Prussian  blue.  For  landscape  work  this 
blue  is  used,  perhaps,  more  than  any  other  colour ;  for  skies 
always,  and  it  enters  into  the  composition  of  the  various 
greens,  and  forms  useful  tints  with  most  of  the  other  pig- 
ments. It  is  not  the  colour  which  an  artist  would  choose  by 
preference  with  which  to  depict  the  tender  tints  of  the  sky, 
for,  truth  to  tell,  it  has  a  greenish  hue,  and  is  rather  cold 
and  repellent  in  character ;  but  it  is  really  the  only  blue 
which  can  be  laid  on  the  glass  in  a  flat,  even  tint,  and 


150 


THE  BOOK  OF  THE  LANTERN. 


therefore  we  must  make  the  best  of  it,  such  as  it  is.  We 
have  a  far  larger  choice  in  yellows,  for  no  less  than  four  of 
the  colours  quoted  are,  in  spite  of  their  names,  yellow  in 
tint.  These  are  Italian  pink,  the  most  useful  of  all ; 
Raw  sienna,  not  nearly  so  pure  a  colour;  Yellow  lake, 
rather  a  difficult  colour  to  work  with ;  and  Chinese 
orange,  a  most  valuable  and  rich  tint.  Brown  pink  may 
also  be  described  as  a  yellow,  and  brown  madder  has  also  a 
great  deal  of  the  same  colour  in  its  composition.  The  reds 
represent  a  great  difficulty  to  the  slide-painted,  for,  although 
they  appear  to  be  very  rich  when  spread  on  canvas,  they  are 
very  weak  colours  when  we  come  to  look  through  them  in 
a  transparency.  It  is  next  to  impossible  to  produce  a  real 
scarlet  as  a  transparent  colour,  but  the  nearest  approach  to 
it  can  be  made  by  using  Chinese  orange  mixed  with  crimson 
lake.  A  great  variety  of  browns  may  be  obtained  by  com- 
bining burnt  sienna  with  the  other  colours,  and  the  ivory 
black  will  be  found  most  useful  in  this  service.  The  best 
brushes  for  general  work  are  those  of  camel-hair,  which 
have  the  further  advantage  of  being  cheap.  But  a  few 
sables  will  be  wanted  for  delicate  markings. 

A  thing  of  first  importance  is  the  selection  of  a  suitable 
medium  with  which  to  mix  the  tints.  Canada  balsam  in 
turpentine  is  of  great  value.  Another  good  one,  which  I 
believe  many  slide -painters  use  almost  exclusively,  is  made 
by  diluting  copal  varnish  with  turpentine,  while  for  dark 
colours,  japanners'  gold  size,  diluted  in  the  same  way,  is  an 
excellent  medium,  and  is  of  special  use  in  the  foreground, 
The  colour  should  be  mixed  up  on  the  palette  with  the 
medium  selected  with  a  proper  palette-knife,  so  as  to  form 


THE  BOOK  OF  THE  LANTERN. 


151 


what  is  in  reality  a  coloured  varnish ;  and  this  must  be 
quickly  applied  to  the  picture  before  it  has  time  to  thicken 
by  evaporation  of  the  solvents. 

For  greens,  to  be  used  mostly  in  foliage  and  for  grass, 
yellow  and  blue  must  be  mixed  together  in  varying  pro- 
portions. There  is  no  such  thing  as  a  satisfactory  trans- 
parent green  which  can  be  bought  ready  made,  and  suit- 
able for  the  purposes  of  the  slide-painter ;  but  the  use  of 
the  two  colours  named,  if  we  take  care  to  vary  the  pro- 
portion of  each,  can  be  made  to  give  a  great  variety  of 
tints.  But  it  should  be  pointed  out  that,  if  used  alone,  this 
compounded  green  will  be  far  too  raw,  and  will  exhibit  a  tint 
which  is  never  seen  in  nature. 

We  mix,  therefore,  with  the  yellow  and  blue,  some  red 
or  brown,  to  take  off:  this  rawness.  An  endless  variety  of 
tints  may  be  made  by  taking  three  colours  only,  and  using 
them  in  different  proportions,  and  I  would  advise  the  slide- 
painter  to  mix  some  of  these  tints,  and  put  them  side  by 
side  on  a  bit  of  glass,  with  a  ticket  attached  to  each 
describing  their  constituents.  This  specimen  glass  will  be 
useful  for  future  reference.  I  give  in  the  next  chapter  a 
few  compound  tints,  which  can  be  made  easily,  and  can  be 
used  for  foliage,  etc. 

The  list  of  colours  given  will  be  found  more  than 
sufficient  for  all  needs,  and  many  slide-painters  do  very 
good  work  with  only  half  their  number,  for  there  is  no 
limit  to  the  number  of  tints  which  one  may  get  by 
judicious  blending.  Mathematicians  are  able  to  tell  us 
the  number  of  chances  against  a  whist-player  turning 
up  the  same  cards  on  two  different  occasions,  and  we 


152 


THE  BOOK  OF  THE  LANTERN. 


know  very  well  that  the  odds  against  such  an  occurrence 
amount  to  an  enormous  figure,  but  no  mathematician 
would  be  able  to  calculate  the  number  of  different  tints 
that  we  can  procure,  even  from  the  three  primary  colours. 
We  have  such  tints  in  the  beautiful  solar  spectrum, 
but  there  they  blend  into  one  another  so  gradually  that 
no  eye  can  count  them. 

One  of  the  great  helps  to  success  is  to  observe  the  rule  of 
being  very  sparing  of  both  colour  and  medium  when  dab- 
bing in  the  sky  portion  of  the  picture  ;  but  the  painter  can 
be  more  lavish  with  both  when  he  is  dealing  with  foliage, 
and  any  broad  masses  of  light  or  shade.  Here  he  can 
often  use  a  large  camel-hair  brush,  and  can  mop  in  the 
colour,  only  taking  care  that  he  does  not  go  over  the  out- 
line which  circumscribes  the  particular  portion  of  the 
picture  he  is  working  upon.  In  the  case  of  a  mass  of  foliage, 
let  him  mix  up  the  desired  paint  on  the  palette  with  a 
flexible  palette  knife,  which  he  should  always  have  at  hand. 
This  should  be  done  thoroughly  and  quickly  ;  then  let  him 
take  up  a  moderate  quantity  of  this  colour  in  the  brush  and 
mop  it  on  to  the  surface  of  the  picture.  For  this  class  of 
work  mastic  varnish,  very  much  thinned  with  turpentine, 
forms  a  capital  vehicle.  The  strength  of  this  mixture  may 
be  one  part  of  mastic  to  six  of  turpentine.  This  medium 
keeps  liquid  long  enough  for  careful  manipulation,  and  yet 
it  dries  quickly  in  comparison  with  other  media  which 
might  be  named. 

Photographic  transparencies  are  now  produced  of  such 
varied  tones  that  in  many  cases  it  will  be  found  advisable 
to  leave  portions  of  the  picture  quite  uncoloured.  With 


THE  BOOK  OF  THE  LANTERN. 


153 


chloride  plates  especially  a  very  wide  range  of  tones  can  be 
obtained,  and  practically  the  experienced  worker  can  pro- 
duce a  picture  in  any  colour, — from  black,  ranging  through 
different  changes  of  brown,  to  red ;  and  even  a  blue  picture 
can  be  produced  on  that  type  of  plate.  Tt  is  often  prac- 
ticable to  suit  the  tint  to  the  class  of  subject.  A  woodland 
scene  may  be  toned  a  rich  brown,  for  example ;  and  this 
tone,  which  the  picture  possesses  at  the  outset,  will  prove 
of  great  help  to  the  colourist.  Many  water-colour  painters 
commence  their  work  by  giving  the  surface  upon  which 
they  work  a  yellow-brown  tint,  and,  when  that  is  dry,  they 
commence  the  picture  proper.  It  will  be  readily  seen  that, 
with  a  photographic  picture  toned  in  the  way  described,  the 
slide-colourist  will  work  under  much  the  same  conditions. 
The  object  in  both  cases  is  to  give  a  general  warm  tone  to 
the  picture,  which  cannot  be  blotted  out  even  by  the  most 
careless  and  ignorant  worker. 

It  is  a  good  practice  to  examine  the  slide  in  the  lantern 
as  the  various  stages  of  the  painting  progress,  taking  care 
to  protect  it  from  dust.  For  this  reason  it  should,  before 
being  placed  on  the  lantern-stage,  be  furnished  with  a 
paper  mask  and  a  cover-glass ;  it  may  then  be  slipped  in 
a  mahogany  frame  kept  for  the  purpose.  By  this  exami- 
nation under  the  light  by  which  it  is  ultimately  to  be 
shown  can  we  alone  judge  of  its  defects.  It  is  now  that 
the  dust,  previously  invisible,  becomes  painfully  evident. 
The  beginner  will,  indeed,  be  forced  to  acknowledge  that 
this  is  an  example  of  matter  in  a  very  wrong  place.  He 
sees  up  in  the  sky  of  his  landscape,  which  he  just  now 
thought  would  look  so  very  beautiful,  what  is  apparently  a 


154 


THE  BOOK  OF  THE  LANTERN. 


broomstick  ;  but  careful  examination  shows  that  it  is  only 
a  little  piece  of  hair  about  a  quarter  of  an  inch  in  length, 
which  is  magnified  into  the  size  of  the  useful  domestic 
appliance  just  mentioned,  and,  what  is  more,  these  little 
bits  of  hair  are  very  difficult  to  remove.  We  may  per- 
haps, lift  them  with  our  etching-needle  from  the  paint  in 
which  they  are  embedded,  but  in  doing  so  we  are  pretty 
sure  to  leave  scratches  behind  which  are  almost  as  bad  as 
the  hairs.  Bits  of  dust  are  everywhere,  and  the  only  way 
in  which  their  intrusion  upon  our  work  can  be  avoided  is 
to  devote  a  room  to  this  express  purpose  of  slide-painting. 
It  should  be  uncarpeted  and  uncurtained,  and  should  be 
swept  with  tea-leaves,  or  better  still,  with  damp  saw-dust,  a 
few  hours  before  any  painting  is  attempted.  Its  table  and 
only  chair  should  be  wiped  down  with  a  damp  duster,  and 
the  same  treatment  should  be  applied  to  the  window  ledge, 
or  any  projecting  parts  of  the  wood- work  which  may  be 
near  the  painter  as  he  sits  at  his  work.  The  artist  should 
put  on  a  linen  blouse,  which  is  rigidly  kept  for  this  work. 
All  these  precautions  may  seem  unnecessary,  but  we  must 
observe  them  if  we  want  to  produce  the  best  possible  work. 
I  have  seen  slides,  otherwise  well  executed,  which  were 
quite  spoiled  by  dust,  and  it  is  one  of  the  aggravations  of 
the  slide-painter's  life,  that  dust  always  gets  into  the  sky, 
where,  of  course,  it  is  more  evident  than  in  any  other  por- 
tion of  the  picture. 

Let  the  table  upon  which  the  operator  works  be  placed 
near  a  window,  preferably  under  a  north  light.  This 
table  should  be  wiped  over  with  a  damp  duster  imme- 
diately before  the  work  is  commenced,  and  it  should  be 


THE  BOOK  OF  THE  LANTERN. 


155 


covered  with  a  sheet  of  newspaper,  also  wiped  with  the  wet 
cloth.  The  easel  is  put  in  the  front  centre  of  the  table ; 
on  its  left-hand  side  may  be  placed  the  colours,  while  on 
the  right  the  palette  must  be  within  easy  reach,  together 
with  a  sheet  of  tissue-paper  folded  in  four,  so  as  to  make  a 
kind  of  pad  upon  which  to  wipe  the  brushes.  The  medium 
employed  varies  with  the  particular  colour  which  happens 
to  be  in  use,  but  turpentine  forms  the  basis  of  all.  A 
little  cup  of  turpentine  should  stand  close  to  the  palette,  in 
which  the  brushes  can  be  washed,  previously  to  being 
partially  dried  by  being  stroked  gently  on  the  pad  of 
tissue-paper  before  mentioned. 

Supposing  that  the  picture  upon  which  the  operator  tries 
his  'prentice  hand  is  a  landscape,  the  sky  will  be  the  portion 
of  the  slide  which  will  first  require  his  attention.  Squeeze 
out  from  the  Prussian  blue  tube  a  little  bit  of  colour  about 
the  size  of  a  grain  of  wheat,  for  this  tint  is  so  powerful 
that  a  little  of  it  will  go  a  long  way.  Near  it  place  a  little 
McGilp.  Now  dip  one  of  the  brushes  in  the  turpentine, 
mix  it  on  the  palette  with  the  McGilp,  and  with  sufficient 
colour  to  give  the  strength  of  tint  desired.  Now  paint 
over  the  sky  portion  of  the  picture  with  bold,  even  strokes, 
from  side  to  side.  The  brush  will  leave  plenty  of  markings, 
ugly  ridges  from  right  to  left ;  but  let  these  pass  for  the 
present,  for  we  shall  remove  them  in  the  next  stage  of 
the  process.  The  picture  should  remain  as  it  is  for  a 
minute  or  two,  so  as  to  give  time  for  the  turpentine  to 
partially  evaporate,  when  we  must  proceed  to  the 
operation  of  dabbing.  Dabbers  are  made  of  different 
materials  :  sometimes  it  is  recommended  to  use  a  piece  of 


156 


THE  BOOK  OF  THE  LANTERN. 


fine  wash-leather,  formed  into  a  little  ball  by  cotton  wool 
inside,  tied  np  like  a  small  pad.  I  have  not  found  such  a 
dabber  to  be  satisfactory  in  practice ;  for  the  leather,  how- 
ever fine,  leaves  feathery  marks  upon  the  colour,  which, 
although  they  are  not  readily  seen  on  the  slide,  become 
painfully  evident  when  the  picture  is  magnified  on  the 
screen.  I  myself  tried,  a  short  time  ago,  to  make  some 
special  dabbers  for  this  work,  which  were  composed  of 
gelatine  and  glycerine  moulded  in  a  small  cup  like  an  egg- 
cup.  These  dabbers,  also,  were  not  as  satisfactory  as  1 
could  have  wished,  although  I  found  that  they  were  better 
than  those  of  wash-leather.  The  best  dabber  which  it  is 
possible  to  get  is  the  finger.  This  needs  a  certain  amount 
of  preparation.  The  flesh  of  the  finger  is  covered  with  a 
number  of  little  ridges,  which  we  well  know  make  what 
we  call  finger-marks  on  anything  touched.  These  ridges 
can  be  obliterated  by  rubbing  the  finger  with  pumice-stone 
and  water,  or  by  using  the  pumice-stone  soap,  which  is 
sold  for  the  express  benefit  of  much-soiled  hands.  A 
quicker  plan  is  to  rub  the  finger  a  few  times  on  very  fine 
glass-paper,  when  the  ridges  quickly  disappear.  It  is 
obvious  that  the  operation  of  rubbing  down  must  only  be 
carried  to  a  slight  extent,  or  else  soreness  will  result.  The 
finger  makes  a  far  more  perfect  pad  than  any  artificial  con- 
trivance because  of  its  exquisite  sensibility ;  for  in  using  it 
we  both  see  and  feel  the  progress  of  the  work. 

Commencing  at  the  left-hand  top  corner,  we  dab  with 
the  finger  rapidly  from  side  to  side  of  the  picture  ;  at  first 
it  will  make  ugly  marks,  but  the  turpentine  gradu- 
ally evaporates  as  the  work  proceeds,  and  these  marks 


THE  BOOK  OF  THE  LANTERN. 


157 


blend  into  one  another,  until  they  finally  disappear,  and  we 
have  before  ns  a  flat,  even  tint  of  colour.  The  knack  of 
laying  in  a  sky  cannot  be  gained  without  a  great  deal  of 
practice ;  but  the  operator  may  feel  assured  that  when  he 
has  once  conquered  this  initial  difficulty  half  his  labour 
is  over. 

If  we  merely  want  a  plain  blue  sky, — and  where  the 
amount  of  sky  is  small  it  is  often  expedient  that  this  should 
be  the  case, — we  can  consider  this  portion  of  our  picture 
finished  with  the  dabbing  ;  but  if  we  want  to  indicate 
clouds,  this  must  be  done  before  the  colour  has  commenced 
to  dry.  Here  comes  in  the  work  of  the  artist.  From  what 
I  have  seen  exhibited  in  the  shop  windows,  I  conclude  that 
many  slide-painters  classify  clouds  under  two  general 
heads,  namely,  large  masses  called  "feather-bed  clouds," 
and  small  ones,  called  "  bolster  clouds."  These  are  created 
by  means  of  a  leather  stump,  moved  with  a  semicircular 
motion,  by  which  clouds  of  either  pattern  can  be  wiped 
out  to  order.  The  student  of  nature  will,  however,  aim 
at  something  higher  than  this ;  for  he  will  know  that  no 
two  clouds,  of  the  thousands  he  has  gazed  upon,  have  ever 
been  alike.  For  convenience  sake,  meteorologists  write  of 
cumulus,  cirrus,  stratus,  and  nimbus  forms  of  clouds,  but, 
in  reality,  although  each  term  describes  a  typical  form  of 
vapour,  they  convey  very  little  information  to  the  mind's 
eye.  Each  form  so  constantly  blends  with  the  other  to  delight 
the  eye,  that  no  words  can  sufficiently  describe  the  vast 
variety  of  cloud  beauties  presented  to  us.  In  attempting 
to  imL^te  some  of  these  effects  of  nature  in  glass-painting, 
I  find  that  a  piece  of  kid  wrapped  round  a  pointed  stick 


158 


THE  BOOK  OF  THE  LANTERN. 


is  far  more  serviceable  than  an  ordinary  leather  stump 
The  rough  side  of  the  leather  should  be  used  as  the  rub 
bing  surface,  and,  by  altering  its  position  on  the  stick, 
sometimes  letting  a  soft  ragged  edge  touch  the  paint  where 
a  fleecy  cloud  is  to  be  described,  and  sometimes  using  the 
material  tightly  stretched  over  its  support  where  bold 
touches  are  necessary,  a  great  number  of  different  effects 
can  be  secured.  The  sky  being  finished,  it  will  be  convenient 
now  to  put  in  any  other  parts  of  the  picture  where  blue 
or  purple  is  required.  The  distant  hills  can  be  covered 
with  the  sky  tint,  mingled  judiciously  with  a  little  crimson- 
lake.  Water,  in  which  the  sky  is  reflected,  will,  of  course, 
be  painted  in  with  the  sky  colour.  Shadows  generally  will 
also  partake  of  the  purple  tint  already  mentioned.  These 
are  all  laid  in  with  the  brush,  as  before  indicated,  and,  time 
having  been  given  for  the  partial  evaporation  of  the  turpen- 
tine, they i  must  be  gently  dabbed  with  the  finger.  No  care 
need  be  taken  about  transgressing  over  other  portions  of 
the  picture  where  blue  or  purple  has  no  business  to  be. 
These  can  be  wiped  clean  with  leather  or  stump,  after  the 
tints  have  been  satisfactorily  laid  in. 


CHAPTER  XII. 


ON  COLOURING    PHOTOGRAPHIC    TRANSPARENCIES   FOR  LANTERN 

slides  (continued). 

GREAT  many  subjects  can  be  advantageously  # 
treated  as  moonlight  pictures,  and  very  attractive 
they  are  if  well  done.  In  this  case,  the  blue 
must  be  laid  on  of  a  much  darker  hue,  and  can  have 
blended  with  it  a  little  ivory-black.  Having  decided 
upon  the  best  position  for  the  "  queen  of  night,"  that 
place  should  be  lightened  by  extra  hard  dabbing,  and 
any  clouds  that  may  be  required  can  be  wiped  out  at 
the  same  time,  taking  care  that  their  light  edges  are 
nearest  to  the  uncreated  moon.  The  moon  must  not 
be  wiped  out,  but  must  be  picked  out,  film  and  all,  so 
that  nothing  but  bare  glass  is  on  the  spot  covered  by  it. 
To  accomplish  this,  wait  until  the  paint  is  bone  dry,  and 
attach  to  the  place  where  the  moon  is  to  be  a  tiny  piece  of 
gummed  postage-stamp  paper.  This  should  not  be  bigger 
than  a  small  pea,  and  is  merely  for  the  temporary  purpose 
of  holding  the  leg  of  a  small  pair  of  compasses.  I  keep  a 
special  pair  for  this  particular  work,  one  leg  being  ground 


160 


THE  BOOK  OF  THE  LANTERN. 


so  as  to  form  a  cutting  edge.  Having  opened  the  compass 
to  the  required  distance,  plant  one  point  on  the  paper,  and 
gradually  with  the  other  cut  through  the  gelatine  film. 
The  circular  disc  so  marked  out  can  now  be  quickly  picked 
away,  bit  by  bit,  with  the  etching-needle.  (This  needle, 
by  the  way,  is  merely  an  ordinary  needle,  bound  to  a  pen- 
holder by  waxed  thread.)  The  same  instrument  can  be 
used  afterwards  for  picking  out  effective  lights  in  the  fore- 
ground ;  but  the  great  fear  is  that  the  beginner  should 
abuse  the  power  thus  put  into  his  hands.  The  touches 
should  be  of  the  most  minute  description,  and  the  operator 
should  constantly  remember  that  his  work,  with  all  its 
faults,  has  to  be  magnified  to  a  very  great  extent. 

I  need  hardly  point  out  that  a  most  effective  change  can 
be  made  by  showing  a  landscape,  first  coloured  as  a  day- 
light picture,  and  then  dissolving  it  into  the  same  view  by 
moonlight.  This  change  requires  a  double  dissolving-view 
lantern,  the  daylight  picture  being  placed  in  one  lantern, 
while  the  moonlight  picture  is  placed  in  the  other,  care 
being  taken  that  both  pictures  register;  that  is  to  say, 
occupy  exactly  the  same  position  on  the  sheet  upon  which 
the  images  are  projected. 

But  let  the  beginner  not  attempt  sunsets  of  the  gorgeous 
order,  after  the  manner  of  G.  M.  W.  Turner  (deceased), 
until  great  practice  has  taught  him  the  different  character- 
istics of  his  colours.  I  do  not  here  allude  to  their  tone 
character,  but  to  the  different  ways  they  behave,  mechani- 
cally, when  applied  to  the  slippery  surface  of  the  picture, 
and  the  different  media  required  to  coax  them  into  lying 
flat.  He  may  think  that,  because  he  knows  how  to  produce 


THE  BOOK  OF  THE  LANTERN. 


161 


a  good  even  sky-blue  tint,  he  has  only  to  try  the  same  pro- 
cedure with  his  yellows  and  reds  to  produce  all  kinds  of 
brilliant,  ethereal,  striped-petticoat  effects.  But,  on  trying 
these  colours,  he  will  soon  find  out  his  mistake,  and  will 
also  find  that  he  must  add  varnish  to  them  before  he  can 
work  with  them  at  all.  Moreover,  they  seem  to  be  espe- 
cially prone  to  attract  any  little  unconsidered  trifles  in  the 
way  of  dust  which  may  be  seeking  rest.. 

1  was  so  impressed  with  these  difficulties  with  regard  to 
sunset  skies,  when  first  I  began  glass  painting,  that  1  sought 
for  another  means  altogether  for  gaining  what  I  wished. 
I  was  attracted  by  the  brilliant  hues  of  the  aniline,  or  coal- 
tar  colours,  and  at  once  endeavoured  to  enlist  them  into  my 
service.  As  others  may  be  tempted  to  work  in  the  same 
groove,  I  may  at  once  state  why,  after  patient  trial,  I  dis- 
carded them.  Most  of  these  colours  can  be  readily  dissolved 
in  alcohol,  and,  therefore,  it  is  not  difficult  to  make 
coloured  varnishes  with  them.  But  when  I  tried  to  paint 
my  gelatine  picture  with  the  splendid  tints,  I  found  it  next 
to  impossible  to  confine  them  within  the  boundaries  of  any 
outlines  whatever.  They  would  flow  over  the  edges  on 
their  own  account,  do  what  I  might.  The  fact  is  that  these 
aniline  colours  have  a  kind  of  greedy  affinity  for  gelatine, 
and  there  seem  to  be  no  means  of  controlling  their  advance 
when  once  they  come  into  contact  with  it.  By  flooding 
an  entire  picture  with  a  yellow  or  red  varnish,  I  was  able 
to  gain  (sometimes)  some  wonderful  effects.  But  the  action 
of  the  dye  upon  the  gelatine  was  of  too  uncertain  a  nature 
to  tempt  me  to  adopt  that  method  of  working  as  a  perma- 
nent resource.    Lastly,  aniline  colours  are  fugitive, 

M 


162 


THE  BOOK  OF  THE  LANTERN. 


Hitherto  I  have  regarded  the  picture  as  possessing  a 
plain  glass  surface  to  represent  the  sky,  and  this  will  be 
found  to  be  the  case  with  most  photographic  slides.  But 
we  all  know  that  a  plain  white  sky  in  a  photograph  is,  from 
an  artistic  point  of  view,  an  abomination.  By  the  simple 
process  of  colouring  we  get  over  the  difficulty ;  still,  if  we 
can  produce  upon  a  photographic  transparency  natural 
clouds  either  existing  in  the  original  negative  by  the  virtue 
of  a  properly-constructed  shutter,  which  will  only  give  a 
fraction  of  the  normal  exposure  to  the  sky,  or  by  a  system 
of  printing-in  from  a  separate  negative  in  a  way  that  need 
not  be  described  here,  it  will  be  a  great  artistic  gain.  In 
colouring  such  a  sky  the  painter  has  a  great  advantage,  for 
irregularities  in  laying  on  the  colour,  which  would  other- 
wise be  distinctly  visible,  are  hidden  by  the  details  of  the 
clouds  in  the  picture. 

In  colouring  such  a  sky  we  may  commence,  as  usual,  by 
dabbing  on  the  blue  in  the  spaces  which  represent  rifts 
between  the  clouds,  and  we  can  then  add  tender  tints  made 
up  by  mingling  such  colours  as  crimson  lake,  and  the 
various  yellows  at  our  disposal,  and  we  can  also  add  to  the 
richness  of  the  general  effect  by  putting  in  different  tones 
of  lavender,  mauve,  and  purple,  made  up  with  crimson  lake, 
the  madders,  and  blue.  These  colours,  after  the  blue  has 
been  dabbed  on,  can  best  be  painted  in  with  the  brush, 
using  as  a  medium  Canada  balsam  in  turpentine.  This  is 
a  good,  quick-drying  medium,  and  it  has  the  advantage  of 
being  so  pale  in  colour  that  it  will  not  effect  the  most  deli- 
cate tints. 

Before  proceeding  farther  with  the  work,  the  picture 


THE  BOOK  OF  THE  LAMERN. 


163 


should  be  dried  by  heat, — and  there  are  many  means  of 
doing  this.  An  oven,  not  too  hot,  w  ill  do  what  is  neces- 
sary, but  it  is  uncertain,  for  the  heat  may  rise  to  such  a 
pitch  that  picture,  gelatine,  and  all  will  curl  off  the  glass. 
A  tin  biscuit  canister,  divided  into  grooves,  and  placed 
(dutch  oven  fashion)  in  front  of  a  good  clear  fire  is  better  ; 
but  the  best  plan  that  I  have  tried  is  the  following  :  place 
the  glasses  to  be  dried  upon  a  flat  iron  plate  above  a  gas 
stove,  the  heat  of  which  can  be  regulated.  Upon  the  top 
of  the  plate  put  a  frame  of  wood,  covered  with  fine  muslin, 
to  keep  off  the  dust.  About  twenty  minutes  of  such  treat- 
ment will  make  the  layer  of  paint  on  the  glass  so  hard 
that  it  can  be  worked  upon  with  other  colours,  or  sub- 
mitted to  the  moonlight  operation  as  already  described.  It 
is  during  the  operation  of  laying  in  the  sky,  &c,  which  may 
be  comprehended  under  the  term  "  first  painting,"  and  the 
subsequent  drying,  that  access  of  dust  must  be  carefully 
guarded  against. 

Lantern  slides,  by  whatever  photographic  process  they 
may  have  been  produced,  will  stand  a  great  deal  of  heat, 
and  they  can  be  made  hotter  than  the  hand  can  con 
yeniently  bear  with  impunity.  This  heat  may  be  con- 
tinued for  about  half  an  hour,  and  it  will  be  found  that 
it  has  a  kind  of  japanning  effect  upon  the  oil  colours 
employed;  indeed,  the  colours  are  by  this  means  made  so 
hard  that  it  is  difficult,  if  not  impossible,  to  remove  them 
afterwards  without  at  the  same  time  destroying  the  photo- 
graphic image  beneath  the  pigment. 

After  the  sky  has  been  dried  in  the  manner  described,  it 
can  easily  be  deepened,  if  found  necessary,  by  the  applica- 

x  2 


164 


THE  BOOK  OF  THE  LANTERN. 


tion  of  a  little  more  paint,  which  need  not  be  applied  with 
a  brash,  but  can  be  simply  dabbed  on  with  the  finger. 
Some  very  good  effects  are  often  possible  by  this  second 
painting,  especially  when  the  sky  is  deepened,  in  the 
manner  described,  at  its  upper  part  or  zenith ;  such  a 
deepening,  it  will  be  readily  seen,  being  in  strict  accordance 
with  the  sky  of  nature. 

A  blue  sky  with  white  clouds  formed  by  the  simple 
operation  of  wiping  out  the  colour,  and  leaving  the  clear 
gelatine,  is  by  far  the  easiest  kind  of  sky  to  produce.  It  can 
be  modified  in  various  ways  by  working  other  colours  upon 
it  near  the  horizon, — such  as  red  or  black,  most  sparingly 
bestowed,  or  the  zenith  tint  can  be  strengthened  after  the 
slide  has  been  dried.  A  most  effective  sky  is  that  which  I 
may  call  the  ordinary  summer  twilight  sky, — that  is  to  say, 
the  deep  blue  at  the  zenith,  fading  gradually  to  a  lighter  tint 
until  it  merges  into  bright  yellow  or  orange  at  the  horizon. 
Such  a  sky  is  not  difficult  to  produce.  The  best  way  will 
be  to  commence  at  the  horizon  by  dabbing,  without  the 
use  of  the  brush,  Italian  pink  on  to  the  glass ;  a  very  little 
colour  being  applied  to  the  finger,  with  the  addition  of  the 
merest  trace  of  medium,  such  as  Canada  balsam,  in  turpen- 
tine. This  must  be  diligently  dabbed  upon  the  glass  until 
its  stickiness  almost  disappears,  and  its  upper  margin  is 
left  without  any  hard  lines.  Then  the  finger  should  be 
washed  in  the  cup  of  turpentine  which  the  painter  should 
always  have"  at  his  elbow,  and  the  blue  may  be  applied  to  the 
upper  part  of  the  picture  in  the  ordinary  way,  and  dabbed 
down  until  it  almost  touches  the  yellow  which  has  been 
previously  laid  on.    Once  more  wash  and  dry  the  dabbing 


THE  BOOK  OF  THE  LANTERN. 


165 


finger,  and  then  use  it,  without  any  fresh  application  of 
paint,  to  merge  the  two  colours  into  one.  In  this  way 
it  will  be  found,  after  a  little  practice,  that  a  good  junction 
can  be  made,  and  that  one  colour  will  exhibit  a  regular 
gradation  into  the  other.  If  this  work  is  well  done,  the 
effect  will  be  found  to  be  a  most  pleasing  one,  and  should 
not  be  meddled  with  by  the  addition  of  clouds. 

Our  painting  has  now  progressed  to  a  certain  stage.  The 
sky  has  been  laid  in,  the  clouds  have  been  wiped  out,  and 
the  shadows  have  received  a  delicate  purple  tint.  The 
whole  has  been  submitted  to  a  baking  operation,  by  which 
the  attached  colours  are  made  so  hard  and  firm,  that  it 
would  be  difficult  to  remove  them  without  destroying  at  the 
same  time  the  gelatine  film  upon  which  they  are  superposed. 
We  now  place  this  unfinished  sketch  again  upon  the  glass 
easel,  and  will  endeavour  to  turn  it  into  a  finished  picture. 
It  is  at  present  what  Mr.  Whistler  would  call  "  an  arrange- 
ment in  purple  and  blue."  We  will  endeavour,  by  working 
over  these  tints  where  required,  and  by  adding  others,  to 
produce  a  general  harmony  of  effect,  as  nearly  approaching 
to  nature  as  possible. 

Any  one  possessing  artistic  feeling, — and  no  one  without 
that  faculty  will  make  a  really  good  slide-painter,  although  he 
may  easily  come  up  to  a  common  standard, — will,  on  first 
looking  at  the  subject  for  colouring,  make  up  his  mind  as 
to  the  way  in  which  he  means  to  treat  it.  He  will  arrange 
to  have  a  cloud  mass  in  one  place, — possibly  to  relieve  a 
church  steeple  or  other  high  building, — or  a  bright  horizon 
where,  possibly,  lights  are  to  be  seen  through  tangled 
masses  of  foliage  ;  or  in  other  ways  he  will  have  in  his 


166 


THE  BOOK  OF  THE  LANTERN. 


mind  a  definite  programme  to  follow  ont,  and  will  do  his 
best  to  achieve  it,  and  will  do  so  with  more  or  less 
success.  But,  through  all,  he  must  bear  in  mind  that  his 
picture  will  eventually  be  highly  magnified,  and  that  the 
k*ast  blemish  will  be  magnified  too.  In  no  art,  perhaps, 
cexq  a  man  learn  more  by  repeated  failures  (failures 
which  should  be,  from  time  to  time,  submitted  to  the 
searching  light  of  the  lantern)  than  he  can  in  this  art 
of  slide -pain  ting. 

The  worker  must  constantly  remember  that  the  effective- 
ness of  his  picture  is  dependent  far  more  upon  contrast 
than  upon  the  tone  of  any  particular  tint.  Without  con- 
trast his  colours  will  be  meaningless  and  poor,  although, 
individually  they  may  present  brilliant  hues.  The  rule 
governing  contrast  of  painters'  colours, — i.e.,  colours  which 
are  complimentary  to  one  another,—  is  most  simple.  Here 
it  is  in  a  nutshell.  The  three  primary  colours  are  red,  blue, 
and  yellow.*  Any  two  of  these  mixed  together  form  a 
secondary  colour  which  is  complimentary  to  the  remaining 
'primary.  For  example  : — Red  and  blue  mingled  form 
purple.  What  better  contrast  to  purple  can  there  be  than 
yellow, — its  complimentary, — being  the  primary  which  is 
left  out  of  the  combination  ?  Again,  blue  and  yellow  form 
green,  and  green  is  complimentary  to  red.  Once  more, 
yellow  and  red  form  orange,  the  complimentary  of  blue. 
I  have  no  hesitation  in  saying  that  a  man  possessing  this 
little  bit  of  elementary  knowledge  is  far  more  likely  to 


*  This  is  not  correct  for  coloured  light,  but  answers  for  painters* 
pigments. 


THE  BOOK  OF  THE  LANTERN. 


167 


produce  an  effective  picture  with  three  colours  than  can 
one  ignorant  of  it,  although  he  may  have  the  run  of  all 
the  artists'  colour-shops  in  the  kingdom.  He  can  never  go 
far  wrong  if  he  will,  so  far  as  the  subject  will  allow,  place 
green  against  red,  orange  near  blue,  and  yellow  in  conjunc- 
tion with  purple.  A  subject,  such  as  an  Oriental  street- 
scene  or  bazaar,  where  such  combinations  can  be  made 
without  stint,  has  a  most  gorgeous  effect  when  projected 
upon  a  screen.  Each  of  these  colours  can  at  the  same  timt 
be  mingled  to  give  an  endless  range  of  tints, — in  fact,  all 
the  colours  of  the  rainbow.  And  now  let  me  give  a  few 
hints  as  to  finishing  colours  and  combinations  useful  for 
special  purposes,  together  with  the  best  media  with  which 
to  mix  them.  In  these  finishing  colours  the  dabber,  except 
in  extreme  cases,  must  be  relinquished,  and  the  brush 
(camel  hair  and  sable)  alone  employed. 

Skies  and  Clouds. — Prussian  blue  (some  prefer  Chinese 
blue),  rose  madder,  purple  madder,  Italian  pink.  The  blue 
to  be  laid  on  as  already  described,  using  as  a  medium 
McGilp  and  turpentine.  In  laying  on  after  tints  a  small 
quantity  of  copal  varnish  should  be  added. 

Water  always  reflects  the  colours  above  it.  If  the  water 
be  very  still,  the  effect  of  surface  may  be  given  to  it  by 
drawing  gently  across  it  a  dry  (mop)  brush,  such  as  gilders 
use.  In  brooks  and  running  streams,  lights  may  be  picked 
out  while  the  colour  is  wet,  with  a  pointed  stick,  or  when 
dry  with  the  etching-needle.  In  representing  rough  sea, 
we  must  remember  that  such  water  not  only  reflects  the 
colour  of  the  sky  above  it,  but  shows  also  its  local  colour. 
It  may  first  be  painted  over  with  the  sky  colour,  and,  after 


168 


THE  BOOK  OF  THE  LANTERN. 


baking  and  drying,  this  can  be  worked  upon  with  various 
shades  of  yellow,  blue,  brown  madder,  and  indigo  ;  medium 
Canada  balsam  varnish,  McGilp,  and  turpentine. 

Boats  and  Shipping. — Black,  raw  sienna,  Vandyke 
brown,  burnt  sienna,  Chinese  orange,  indigo, — indeed, 
nearly  all  the  colours  available.    Medium,  same  as  last. 

Foliage. — For  foliage  we  are  limited  for  our  greens  to  a 
mixture  of  Prussian  blue  and  the  various  yellows,  namely, 
Italian  pink,  raw  sienna,  and  brown  pink.  But  these  will 
give  endless  variety  of  tones,  particularly  when  aided  by 
other  colours.    Here  are  a  few  examples : — 

Bkr,  Italian  pink,  and  burnt  sienna. 

Italian  pink,  Vandyke  brown,  and  indigo. 

Italian  pink  and  brown  madder. 

Brown  madder,  Italian  pink,  and  indigo. 

By  adding  Chinese  orange  to  any  of  these,  autumnal 
effects  are  readily  obtained.  Media,  Canada  balsam  var- 
nish )  and  for  the  darker  colours,  gold  size.  N.B. — These 
various  combinations  should  be  made  up  on  the  palette, 
as  required,  with  the  help  of  the  palette  knife. 

Foreground.  — It  is  here  that  the  artist  can  employ  all 
the  treasures  of  his  palette.  Let  him  remember  that  any 
particular  colour  can  be  easily  modified  by  glazing  another 
colour  over  it.  This  is  done  after  the  first  colour  is  dry 
by  mixing  a  second  tint,  which  may  be  applied  above  it. 
The  medium  for  this  varnish  will  vary  with  the  glazing 
colour  employed,  Canada  balsam  will  do  for  most,  but 
where  reds  are  used,  which  are  slow  driers,  the  medium 
should  be  gold  size. 

Let  the  painter  ever  remember  that  force  of  colour  can- 


THE  BOOK  OF  THE  LANTERN. 


169 


not  be  obtained  by  piling  on  masses  of  pigment,  which  will 
naturally  serve  to  obscure  the  details  of  the  photograph 
upon  which  such  pigment  is  placed ;  but  this  force  of 
colour  can  be  easily  produced  by  judicious  contrast  of  differ- 
ent tints.  As  I  have  before  observed,  the  student  must 
make  himself  master  of  the  art  of  colouring,  if  possible, 
before  he  commences  its  practice.  Some  years  ago  there 
was  published  an  excellent  series  of  little  books,  costing 
only  a  few  pence  each,  giving  chromo-lithographic  examples 
of  various  simple  studies  in  water-colour  painting  by 
Callow  and  other  artists,  under  the  title  of  "  Yere  Foster's 
Drawing  Books."  These  books,  I  believe,  are  still  to  be 
had, — at  least,  I  hope  so,  for  they  are  full  of  merit,  and 
give  more  valuable  instruction  than  many  works  of  far 
more  pretension.  They  give  specimens  of  water-colour 
sketches,  unfinished  and  finished,  side  by  side.  Perhaps 
the  former  are  the  more  valuable  for  our  present  purposes, 
for  they  exhibit  merely  broad  masses  of  colour,  and  show 
how  one  tint  can  be  made  to  contrast  with  another.  It 
will  be  seen  in  some  of  these  pictures  that  a  blue  sky  is 
contrasted  with  orange  yellows  in  the  landscape  beneath ; 
and  how,  on  the  other  hand,  a  yejlow  sky  can  be  rendered 
at  once  effective  by  purple  hills  upon  which  it  seems  to 
rest. 

When  the  picture  is  entirely  finished,  it  may  be  once 
more  submitted  to  the  baking  operation,  taking  care  that 
the  heat  never  rises  to  blistering  point,  or  all  the  labour 
spent  on  the  slide  will  be  thrown  away.  The  picture  may 
now  again  be  placed  on  the  easel,  and  if  the  artist  has 
sufficient  reliance  upon  his  power  of  knowing  when  to  stop 


170 


THE  BOOK  OF  THE  LANTERN. 


he  may  with  advantage  take  up  the  etching-needle ;  some- 
times a  single  touch  of  this  magic  wand  will  much  improve 
a  picture.  In  forest  scenery,  for  instance,  a  light  on  a 
trunk,  or  on  a  protruding  branch,  will  make  the  one  or  the 
other  to  stand  out  almost  stereoscopically.  Now  and  then 
too  a  little  spot  or  two  may  be  picked  out  of  the  foliage 
itself.  But  not  in  the  manner  I  lately  saw  in  an  exhibited 
slide,  where  curly  lines,  after  the  drawing-master  style  of 
former  days,  were  made  to  describe  the  edges  of  the  trees 
in  every  direction.  This  was  actually  perpetrated  upon  a 
good  photograph,  and  represents  the  worst  instance  of 
"  painting  the  lily  "  which  I  have  had  the  misfortune  to 
come  across. 


CHAPTER  XIII. 


DESCRIPTION  OF  VARIOUS  EXPERIMENTS, — CHEMICAL,  ELECTRICAL, 
ETC., — FOR  CLASS  INSTRUCTION,  WHICH  ARE  POSSIBLE  WITH 
THE  LANTERN. 


OR  different  experiments,  various  forms  of  slides 
must  be  employed.  The  galvanometer  slide, 
shown  at  fig.  45,  is  an  extremely  useful 
one  for  demonstrations  in  electricity  and  magnetism. 
I  need  hardly  mention  that  such  a  slide  consists  of 
a   magnetised  needle,  which  is  surrounded   by  a  coil 


Fig.  45. 

of  fine  wire.    This  coil  is  flattened,  and  there   is  just 

space   enough   between  its  convolutions  for  the  needle 

to    move    from    side    to    side.     It  is  supported  on 


172 


THE  BOOK  OF  THE  LANTESN. 


a  central  pin,  which  is  shown  bj  the  screw  slit  in  the  cut. 

A  pane  of  glass  of  a  semicircular  shape  forms  a  back- 
ground for  the  needle ;  and  this  glass  can  either  be  left 
plain,  as  in  the  illustration,  or  it  can  have  drawn  upon  it  a 
scale.  The  slide  figured  is  without  the  arrangement  just 
mentioned,  and  it  is  one  that  I  have  employed  for  a  special 
purpose.  I  have  used  it  as  a  means  of  demonstrating  the 
action  of  the  needle  telegraphic  instrument;  and  it  will 
be  noticed  that  two  little  buttons  are  fastened  to  the 
glass  in  order  to  prevent  the  needle  making  too  wide  an 
excursion. 

It  may  be  mentioned  here  for  the  benefit  of  those  who  • 
are  unused  to  electrical  instruments,  that  a  galvanometer 
furnishes  the  means  of  detecting  the  existence  of  an  elec- 
tric current.  In  its  higher  forms  it  is  so  sensitive  that 
a  current,  generated  by  touching  two  dissimilar  metals 
with  the  fingers  and  excited  by  the  natural  warmth  of  the 
band,  can,  by  a  galvanometer,  be  made  evident  to  the  eye. 
The  most  simple  form  of  galvanometer  can  be  readily 
made  from  one  of  those  little  charm  compasses  which  are 
sold  at  the  opticians'  for  about  Is.  each.  Take  such  a 
compass,  and  bind  it  across  with  several  layers  of  fine  silk- 
covered  copper  wire.  Place  it  in  such  a  position  that  the 
wire  coil  lies  parallel  with  the  needle,  which  will,  of  course, 
be  north  and  south  ;  now  join  the  entls  of  the  wire  to 
any  form  of  electric  battery,  and  the  needle  will  imme- 
diately swing  round  and  take  an  east  and  west  direction. 
By  changing  the  position  of  the  wires  with  regard  to  the 
poles  of  the  battery,  it  will  be  noticed  that  the  needle  is 
deflected  in  the  opposite  direction.     These  phenomena 


THE  BOOK  OF  THE  LANTERN. 


173 


form  the  basis  of  the  single  needle  electric  telegraph,  and 
it  is  to  demonstrate  the  powers  of  that  telegraph  that  the 
lantern  galvanometer,  which 
is  here  figured,  has  been 
devised.  It  will  be  noticed 
that  on  its  right-hand  side  it 
is  furnished  with  two  ter- 
minals. These  are  connected 
with  the  ends  of  the  coil 
wire,  and  provide  a  means  of 
readily  joining  the  instrument 
up  to  the  battery,  placed  in 
any  position  outside  the  lantern  ;  but  in  practice  it  will 
be  found  advisable  to  also  place  in  connexion  with  this 
slide  and  its  battery  a  little  piece  of  apparatus  which  may 
be  called  a  "current  reverser,"  which  can  easily  be  made 
at  home.  It  is  shown  in  fig.  46.  It  consists  of  two 
little  treadles  formed  out  of  brass.  This  brass,  it  may 
be  mentioned,  should  be  of  the  hard-rolled  kind,  such  as 
is  used  for  springs. 

Each  of  these  little  treadles  is  fastened  down  to  a  maho- 
gany b  rd,  which  forms  the  base  of  the  instrument,  and 
each  OxiO  is  in  connexion  with  a  terminal  screw,  which  is 
indicated  in  the  cut  by  a  round  dot.  Across  the  other  end 
of  the  treadles  is  a  raised  bar  of  brass,  against  which  they 
spring  up  and  touch  when  in  their  normal  condition ;  but 
when  either  of  them  is  pressed  down,  it  touches  a  piece  of 
brass  wire  which  is  let  into  the  top  of  the  mahogany  board 
immediately  underneath. 

This  wire,  as  well  as  the  piece  of  brass  just  mentioned, 


in 


THE  BOOK  OF  THE  LANTERN. 


is  connected  with  its  own  terminal ;  these  two  latter  ter- 
minals in  the  cnt  being  lettered  bb,  and  signifying  that 
they  should  be  joined  up  to  the  battery  employed.  The 
other  two,  which  are  lettered  gg,  are  fastened  to  the 
terminals  on  the  galvanometer  slides. 

In  practice  it  is  best  for  the  current  reverser  to  be  placed 
on  the  lecturer's  desk,  at  some  distance  from  the  lantern, 
while  the  galvanometer  slide  is  joined  up  by  means  of  tem- 
porary wire  connexions.  The  lecturer  then  has  the  power 
of  reversing  the  current  by  touching  with  his  finger  either 
of  the  two  treadles,  and  he  can  demonstrate  in  the  most 
perfect  manner  how  the  different  letters  in  the  tele- 
graphic alphabet  are  made  up  of  movements  of  the  needle 
to  the  right  or  left,  as  the  case  may  be.  He  can  also  point 
out  that  the  "  dots  "  and  "  dashes  "  of  the  Morse  system 
correspond  with  these  right  and  left  hand  movements  of 
the  magnetic  needle. 

In  the  old  days  of  the  Polytechnic  Institution  in  Regent 
Street,  which  was  the  resort  of  so  many  delighted  schoolboys 
and  girls,  there  were  several  experiments  performed  with  the 
lantern  which,  so  far  as  I  know,  have  not  been  repeated 
lse where.  One  of  the  most  curious  was  the  movements  of 
the  legs  of  a  frog.  This  is  rather  a  difficult  experiment  tc 
perform,  but  when  well  done,  is  highly  effective  on  the 
screen. 

At  the  Polytechnic  the  frog's  legs  covered  the  large 
screen,  and  were  thus  magnified  to  about  26  feet.  The  legs 
were  hung  to  a  special  form  of  slide,  and  the  nerves  and 
muscles  of  the  dead  frog  were  touched  with  metallic  wires, 
when  they  immediately  kicked  out  in  the  most  startling 


THE  BOOK  OP  THE  LANTERN. 


175 


manner.  The  importance  of  this  experiment,  as  a  demon- 
stration, will  be  acknowledged  when  it  is  remembered  that 
this  movement  of  a  frog's  legs,  accidentally  brought  about 
by  Galvani,  laid  the  foundation  of  our  present  knowledge  of 
current  Electricity  or  Galvanism,  as  it  used  to  be  called, 
after  that  first  experimenter. 

Another  most  effective  experiment  was  shown  in  con- 
nection with  a  lecture  upon  the  Suez  Canal  by  Professor 
Pepper.  After  exhibiting  a  number  of  experiments  upon 
sand,  and  showing  that  it  always  fell  at  a  certain  angle, 
and  exerted  lateral  instead  of  perpendicular  pressure, 
an  image  of  an  ordinary  hour-glass  was  cast  upon  the 
screen.  This  sand-glass  was  supported  in  a  frame,  and  its 
sides  were  flattened  so  that  it  could  fit  the  lantern  stage.  It 
had  rather  an  amusing  appearance,  because  like  all  instru- 
ments placed  in  the  lantern,  the  image  was  inverted,  and 
the  sand  therefore  appeared  to  flow  upward  instead  of 
downward.  A  curious  fact,  too,  was  noticed  when  this 
familiar  instrument  was  magnified  to  such  an  enormous  ex- 
tent, each  particle  of  sand  was  seen  to  strike  a  blow  upon 
the  top  of  the  cone  above,  and  the  force  from  that  blow 
passed  from  the  point  of  the  inverted  cone  to  its  base,  and 
formed  a  peculiar  wave-like  figure  in  its  passage. 

I  have  never  seen  this  experiment  repeated  elsewhere, 
but  it  is  one  that  should  not  be  forgotten. 

Among  the  experiments  which  can  be  performed  by 
means  of  a  lantern,  and  better  performed, — so  far  as  an 
audience  is  concerned, — than  by  any  other  means,  are 
those  relating  to  cohesion  figures.  Professor  Tomlinson 
was  the  first  to  give  much  attention  to  these  interesting 


176 


THE  BOOK  OF  THE  LANTERN. 


figures,  and  lie  made  many  experiments  in  this  direction. 
He  found  that  almost  all  the  common  oils  and  fats  give 
natural  diagrams  by  which  they  can  be  identified;  and 
further,  that  these  figures  will  vary,  according  to  the  length 
of  time  for  which  the  oil  has  been  exposed  to  the  air.  To 
get  some  idea  of  the  nature  of  these  beautiful  figures,  a 
drop  of  pure  sperm  oil  may  be  allowed  to  fall  on  the  surface 
of  a  pan  of  water.  It  will  be  seen  in  a  few  seconds  that 
the  film  of  oil  will  break  up  into  a  number  of  little  open- 
ings, and  that  it  will  exhibit  a  pattern  of  great  beauty. 
Hape  oil,  Lucca  oil,  and  some  others,  give  patterns  of  en- 
tirely different  designs  ;  some  of  them  very  much  resembling 
beautiful  crochet-work.  In  order  to  show  these  patterns 
in  the  lantern,  we  have  two  or  three  different  methods  of 
going  to  work.  We  can  exhibit  these  cohesion  figures,  for 
instance,  by  the  simple  aid  of  two  pieces  of  clear  glass. 
Between  two  such  plates  put  a  little  vaseline,  which  in 
order  to  increase  the  effect  on  the  screen  may  be  coloured 
red  with  alkanet  root.  The  plates  are  pressed  together,  with 
the  vaseline  between  them,  and  are  then  secured  by  a  ring  of 
india-rubber  at  each  end.  They  are  then  put  into  the  lan- 
tern, and  while  standing  upon  the  lantern  stage  the  blade 
of  a  knife  is  inserted  between  the  two  glasses  and  gradually 
turned  so  that  they  are  slightly  separated.  The  effect 
upon  the  screen  is  very  beautiful,  the  disc  appearing  to  be 
covered  with  arborescent  figures.  This  experiment  may  be 
repeated  more  than  once,  but  the  vaseline  will  require 
renewal  after  a  time.  Another  mode,  and  perhaps  a  better 
one,  of  showing  the  same  phenomena,  is  by  means  of  the 
vertical  attachment  to  the  lantern.    In    this    case  the 


THE  BOOK  OP  THE  LANTERN. 


177 


lantern  slide  must  take  the  form  of  a  shallow  box,  having 
a  glass  bottom.  Such  a  box  can  easily  be  made  by  fit- 
ting a  piece  of  thin  glass,  say,  3  \  inches  square,  into 
a  frame  of  wood  half  an  inch  in  height,  and  cementing 
the  glass  in  a  groove  with  marine  glue.  The  glass 
cell  so  provided  should  be  placed  in  a  horizontal 
position  upon  the  stage,  and  be  filled  with  water.  Dif- 
ferent oils  can  then  be  dropped  on  to  the  surface  of  the 
water,  and  the  characteristic  cohesion  figures  due  to  each 
will  be  thrown  upon  the  screen.  If  this  latter  mode  of 
showing  the  phenomena  be  chosen,  it  is  obvious  that  a 
different  glass  cell  must  be  used  for  each  oil  exhibited, 
and  I  think  that  it  would  be  quite  possible  to  produce 
lantern  slides  direct  from  these  oily  cohesion  figures ; 
although  I  have  not  experimented  in  this  direction  myself. 
The  principle  employed  would  be  that  of  "  Lithography." 
The  oily  figures  might  be  transferred  to  a  piece  of  glass 
direct  from  the  surface  of  the  water.  Those  figures  could 
be  darkened  to  any  extent  by  employing  a  greasy  printing 
ink,  taking  care  to  wet  the  glass  so  as  to  repel  the  ink ; 
but  this  is  a  matter  into  which  I  cannot  now  afford  space 
to  enter,  and  I  merely  allude  to  it  as  a  field  for  profitable 
experiment. 

Many  pieces  of  apparatus  have  been  devised  for  the 
lantern,  which  exhibit  the  principle  of  what  is  known  as 
"  persistence  of  vision."  In  older  that  we  may  thoroughly 
understand  in  what  this  principle  consists,  I  may  men- 
tion that  the  human  eye  possesses  a  peculiar  property 
which  is  highly  convenient  to  its  proprietor.  What  is 
meant  by  "  persistence  "  is  that  the  retina  has  the  power 

N 


178 


THE  BOOK  OF  THE  .LANTERN. 


of  retaining  the  image  of  anything  seen  for  at  least  one- 
eighth  part  of  a  sec  d  after  the  eye  ceases  to  see  that 
object. 

As  an  example  of  this,  let  me  remind  my  readers,  that 
although  in  the  ordinary  course  of  things,  we  are  con- 
tinually "winking,"  an  operation  which  is  necessary  to 
lubricate  the  eyeball,  we  are  quite  insensible  of  the  cir- 
cumstance that  for  the  time  occupied  in  doing  so,  we  are 
placed  in  absolute  darkness.  Although  the  eyelids  are 
closed  and  the  light  is  shut  out,  we  have  no  perception  of 
darkness,  simply  because  of  this  curious  property  possessed 
by  the  retina  of  retaining  the  image  of  the  object  last  seen, 
for  at  least  the  eighth  part  of  a  second.  It  is  for  this 
reason, — I  may  also  point  out  in  passing, — that  so-called 
instantaneous  photographs  of  moving  objects,  such  as  a 
"trotting  horse,"  &c,  appear  to  us  to  exhibit  such  very 
unnatural  attitudes.  As  a  matter  of  fact  the  photographic 
camera  records  movements  which  the  human  eye,  on  account 
of  this  "persistence  of  vision,"  cannot  appreciate.  It  is 
evident  that  if  this  doctrine  be  true,  the  eye  cannot  appre- 
ciate a  movement  which  takes  place  in  less  time  than  the 
eighth  part  of  a  second,  and  it  is  because  the  photographic 
lens  can  grasp  and  record  the  movements  which  take  place 
in  a  mere  fraction  of  that  time,  that  the  attitudes  it  depicts 
appear  to  us  so  highly  unnatural.  The  human  eye  has 
never  seen  such  attitudes,  and  never  will  see  them. 

Perhaps  the  simplest  illustration  of  "  persistence  of 
vision  "  is  afforded  by  a  burnt  stick  with  a  red  hot  end, 
which  is  turned  rapidly  round  in  front  of  the  observer ; 
to  that  observer  the  red  spot  of  light  looks  like  a  con- 


THE  BOOK  OF  THE  LANTERN. 


179 


tmuous  ring  of  fire,  but  we  know  well  enough  that  it  is 
simply  a  spark.  It  is  the  rapid  movement  helped  by  this 
"  persistence  "  of  the  retina,  that  causes  the  spot  of  light  to 
appear  to  us  as  a  continuous  circle.  So  it  is  that  heavy 
rain  drops, — which  we  know  very  well  are  independent 
globules  of  water, — appear  to  be  like  streaks  falling  from 
the  sky,  and  like  streaks  artists  invariably  depict  them. 
And  rightly  so,  too,  for  we  do  not  wish  artists  to  bring 
before  us  representations  of  things  as  the  eye  cannot  see 
them,  but  of  objects  as  they  appear  to  us  under  ordinary 
conditions.  For  this  reason  the  claim  which  has  been  made 
in  some  quarters,  that  the  unusual  attitudes  depicted  by 
instantaneous  photography,  should  be  a  help  to  artists  in 
their  delineation  of  animal  movement,  appears  to  be  ex- 
tremely nonsensical.  Such  attitudes  may  certainly  be 
studied  by  artists,  as  a  means  of  showing  how  the  various 
movements  are  brought  about,  just  as  he  would  study  the 
skeleton  of  a  man,  in  order  to  get  a  better  notion  of  the 
outward  form  of  the  body ;  but  both  should  be  kept  as 
studies,  and  certainly  not  introduced  into  finished  works. 

The  kaleidotrope  consists  of  a  disc  of  perforated  cardboard. 
It  is  supported  on  a  spring  of  wire  in  such  a  manner  that  it 
can  be  rapidly  turned  round  by  the  finger  as  the  frame  in 
which%  it  is  contained  stands  upon  the  lantern  stage.  The 
other  end  of  the  spring  is  cemented  to  a  plate  of  glass  so 
that  the  light  can  easily  travel  through  the  perforations  in 
the  disc  and  be  rendered  evident  on  the  lantern  screen. 
As  this  card  is  struck  with  the  finger  so  as  to  cause  it  to 
move  and  vibrate  on  its  spring  in  different  directions, 
the  spots  of  light  on  the  screen  by  their  movement  assume 

n  2 


180 


THE  BOOK  OF  THE  LANTERN. 


a  great  variety  of  curves.  It  will  be  thus  seen  that  this 
instrument  simply  gives  a  variation  of  the  burnt- stick 
experiment  already  alluded  to. 

Mr.  Beale,  of  Greenwich,  has  invented  a  most  ingenious 
and  amusing  apparatus  for  the  lantern  which  also  depends 
upon  "  persistence  of  vision."  This  is  called  the  choreuto- 
scope,  and  is  made  in  two  different  forms.  In  its  more  elabo- 
rate shape  it  consists  of  a  circular  plate  having  upou  it  figures 
drawn  upon  glass,  and  so  arranged  with  their  limbs  in 
different  attitudes,  zoetrope  fashion,  that  when  one  figure 
is  rapidly  changed  for  the  other,  the  image  seems  to  be  in 
actual  movement.  The  contrivance  is  so  arranged  that 
before  the  figure  actually  changes  a  little  screen  obscures 
it  for  the  moment,  so  that  the  movement  of  the  disc  is  not 
apparent  upon  the  sheet.  Mr.  Beale  has  of  late  years 
simplified  this  instrument.  In  this  case  the  figures  are 
painted  upon  a  slip  of  glass  about  seven  inches  in  length, 
and  by  means  of  a  special  form  of  slide  they  are  rapidly 
brought  in  front  of  the  lens  in  the  manner  just  described. 

The  most  effective  set  of  figures  of  any  is  a  skeleton,  the 
reason  being  that  it  consists  only  of  white  on  black. 
Such  figures  can  therefore  be  cut  out,  stencil  fashion,  in 
a  sheet  of  thin  copper-foil ;  the  openings  in  this  plate  per- 
mitting a  far  larger  amount  of  light  to  reach  the  screen 
than  if  the  figures  were  drawn  upon  glass. 

Another  far  more  perfect  and  elaborate  device  for  illus- 
trating  the   phenomena  connected  with   persistence  o 
vision  is  an  instrument  called  by  the  somewhat  ponderous 
title, — the  Astrometeoroscope.    The  inventor  of  this  clever 
oiece   of  apparatus   was  the    Hungarian  mechanician, 


THE  BOOK  OP  THE  LANTERN. 


181 


S.  Pichler,  who  designed  various  other  ingenious  contriv- 
ances. He  was  very  jealous  about  this  astrometeoroscope, 
and  the  only  one  made  was  at  the  Polytechnic  Institution, 
where  it  was  carefully  kept  under  lock  and  key,  except 
when  in  actual  use.  When  the  apparatus  of  the  institution 
came  to  the  hammer,  I  remember  that  there  was  some 
little  excitement  when  the  astrometeoroscope  was  put  up 
for  sale.  Opticians  and  others  would  have  been  glad  to 
get  hold  of  it,  so  as  to  have  multiplied  it  for  sale.  This  led 
to  a  brisk  competition,  ending  with  Mr.  Pichler  giving  an 
extravagant  price  for  his  own  bantling.  And  in  that  way 
the  secret  remains  in  the  hands  of  a  few  only,  and  perhaps 
it  would  be  unkind  to  divulge  it.  But,'  at  any  rate,  I 
cannot  do  much  harm  by  giving  a  general  idea  of  the  out- 
ward appearance  of  the  instrument  and  its  capabilities. 

The  astrometeoroscope  consists  of  a  narrow  box  thirteen 
inches  in  length,  and  of  such  a  width  that  at  one  end  it 
will  fit  the  stage  of  the  lantern.  At  this  end  it  has  the 
usual  three-inch  disc  opening,  which  is  occupied  by  two 
plates  of  metal  which  are  scored  across  obliquely  with  slits 
and  which  are  superposed  one  on  the  other,  so  that  the 
slits  on  each  cross  one  another  diagonally.  Now  it 
is  clear  that  the  only  places  where  light  can  pierce 
these  plates  of  metal  so  as  to  make  itself  evident  on 
the  screen  is  in  those  places  where  the  slits  on  the  plates 
intersect  one  another.  The  effect  on  the  screen,  therefore, 
whilst  the  instrument  is  quiescent,  is  a  series  of  dots  of 
light  all  over  the  screen,  but  at  regular  distances  from  one 
another.  By  very  ingenious  mechanism  the  two  plates  are 
caused  to  move  to  and  fro  in  contrary  directions,  and  the 


182 


THE  BOOK  OF  THE  LANTERN. 


speed  of  either  can  be  varied  at  will  by  the  operator.  The 
effect  upon  the  screen  is  most  curious,  for  it  seems  to  be 
covered  with  a  lacework  of  geometrical  patterns  which 
constantly  change  their  form. 

A  very  favourite  experiment  with  the  lantern,  but  one 
which  it  is  by  no  means  easy  to  perform,  is  the  decomposi- 
tion of  light  by  means  of  a  prism.  For  the  most  perfect 
effects  the  electric  light  is  necessary,  but  as  this  is  beyond 
the  reach  of  most  of  us, — at  any  rate,  for  the  present, — we 
must  be  content  with  what  can  be  done  with  the  ordinary 
limelight.  The  simplest  way  of  showing  the  spectrum 
with  the  lantern  is  to  remove  the  objective  and  to  place  in 
the  lantern  stage  a  card  with  a  slit  in  it,  as 
I  shown  in  the  cut  (fig.  47).    This  slit  should  be 

BBjfcffiiSt  akout  an  inch  in  length,  and  not  more  than 
H  one-twentieth  of  an  inch  in  breadth.    The  card 
should  be  placed  on  the  stage  of  the  lantern  in  a 

Fig.  47.  noriZOntal  position  and  focussed  upon  the  screen 
in  front.  A  prism  is  then  brought  into  the  path  of  the 
slice  of  light  thus  formed, 
and  it  will  be  so  far  bent 
aside  as  to  exhibit  the 
colours  of  the  spectrum  on 
the  ceiling  of  the  room 

(fig.  48).  Fig.  48. 

The  prism  will  require  a  little  turning  about  before  this 
result  is  arrived  at.  But  at  the  best  this  method  of  show- 
ing the  spectrum  is  but  a  makeshift  one ;  it  presents, 
however,  an  easy  method  of  demonstrating  the  decom- 
position of  white  light.    A  preferable  mode  is  to  use  a 


THE  BOOK  OF  THE  LANTERN. 


183 


bisulphide  of  carbon  prism.  This  takes  the  form  of  a 
stoppered  bottle  with  two  sides  ground  away  and  filled  in 
with  plates  of  glass,  which  are  cemented  to  the  re- 
mainder of  the  bottle.  In  this  way  the  wedge  form 
of  the  prism  is  secured.  The  bottle  is  then  filled  with 
bi-sulphide  of  carbon,  and  such  bottles,  ready  charged,  can 
be  obtained  at  the  opticians'.  A  great  objection  to  them 
is  their  liability  to  breakage,  for  bi-sulphide  of  carbon, 
beyond  being  a  most  inflammable  compound,  has  a  most 
disagreeable  and  pungent  odour. 

In  using  a  prism  of  this  description,  it  is  kept  upright 
and  supported  in  front  of  the  lantern.  The  slit  in  the  card 
must  in  this  case  be  vertical,  instead  of  horizontal,  and  the 
lantern  must  be  placed  at  such  an  angle  with  the  sheet 
that  when  the  spectrum  is  rendered  visible  it  appears  in  a 
central  place  on  the  sheet. 

There  are  several  means  available  for  showing  on  the 
lecture-table  that  the  various  colours  of  the  spectrum  will, 
when  combined,  once  more  form  white  light.  Thus  we 
may  place  in  the  path  of  the  coloured  beam  a  double  con- 
vex lens,  which  will  at  once  bring  the  scattered  rays  to  a 
focus,  and  will  form  a  disc  of  white  light.  We  can  also 
recompose  light  by  collecting  the  coloured  rays  by  means 
of  a  concave  mirror,  when  a  card  held  in  the  focus  of  the 
mirror  will  exhibit  a  brilliant  spot  of  light  free  from 
colour.  Another  method  is  to  use  two  prisms  placed 
against  one  another,  thus — Ay>  when  one  will  neutralise 
the  effect  of  the  other,  and  the  emergent  beam  will  be 
white.  Yet  another  way  of  recomposing  light  is  to  use  a 
number  (generally  seven)  of  plain  mirrors,  which  are  so 


184 


THE  BOOK  OF  THE  LANTERN. 


placed  upon  a  stand  that  they  can  each  be  turned  in  any 
required  direction.  The  spectrum  is  allowed  to  fall  upon 
this  system  of  mirrors,  and  each  one  is  so  turned  upon  its 
axis  that  the  particular  colour  which  it  reflects  is  thrown 
upon  one  spot.  The  collective  images  of  the  various 
colours  then  appears  as  a  white  disc. 

The  methods  thus  detailed  are  all  good,  but  cannot 
readily  be  applied  to  the  lantern.  A  way  of  demonstrating 
the  recomposition  of  light  with  that  instrument  has 
recently  been  published  in  America,  by  Mr.  G.  M.  Hop- 
kins, and  the  following  remarks  are  borrowed  from  him. 
After  detailing  the  various  known  methods  of  recomposing 
light,  he  says  : — "  Besides  these  methods,  the  spectrum  has 
been  recombined  by  whirling  or  rocking  a  prism ;  the  move- 
ment of  the  spectrum  being  so  rapid  as  to  be  beyond  the 
power  of  the  eye  to  follow,  the  retina  receiving  the  impres- 
sion merely  as  a  band  of  white  light,  the  colours  being 
united  by  the  superposing  of  the  rapidly  succeeding 
impressions,  which  are  retained  for  an  appreciable  length 
of  time.  The  engraving  shows  a  device  to  be  used  in 
place  of  the  ordinary  rocking  prism.  It  is  perfectly 
simple,  and  involves  no  mechanism.  It  consists  of  an 
inexpensive  prism,  having  attached  to  a  knob  on  either 
end  a  rubber  band.  In  the  present  case  the  bands  are 
attached  by  making  in  each  a  short  slit,  and  insert- 
ing the  knobs  of  the  prism  in  the  slit.  The  rubber 
bands  can  be  held  by  inserting  two  fingers  in  each  and 
drawing  them  taut.  The  prism  can  then  be  held  in  a 
beam  of  sunlight,  and  with  one  finger  the  prism  is  given 
an  oscillating  motion.    The  band  of  light  thus  elongated 


THE  BOOK  OF  THE  LANTERN. 


185 


will  have  prismatic  colours  at  opposite  ends,  but  the  entire 
central  portion  will  be  white.  To  show  that  the  colours  of 
the  spectrum  pass  over  every  portion  of  the  path  of  the 
light,  as  indicated  by  the  band,  the  prism  may  be  rocked 
very  slowly. 

"By  inserting  four  screw  hooks  in  a  vertical  support,  and 
stretching  the  bands  over  the  hooks,  the  prism  is  adapted 
for  use  with  a  lantern.  The  light  emerging  from  the 
lantern  must  pass  through  a  narrow  slit  to  secure  a  per- 
fect spectrum,  and  between  the  screen  and  the  prism 
should  be  placed  another  screen  with  an  oblong  aper- 
ture, which  will  allow  all  of  the  band  of  light  to  appear 
upon  the  screen,  with  the  exception  of  the  coloured 
extremities.  With  the  prism  supported  in  this  way,  it  is 
an  easy  matter  to  turn  it  slowly  back  and  forth,  showing 
on  the  screen  the  moving  spectrum,  which,  with  the  more 
rapid  movement,  produces  the  pure  white  band  of  light." 

The  recomposition  of  light  can  be  well  shown  in  the 
way  just  described ;  but  perhaps  a  more  ready  and  effec- 
tive, if  not  quite  so  scientific,  a  method  is  to  use  a  coloured 
disc,  fitted  as  a  lantern-slide,  with  a  revolving  arrangement 
similar  to  that  used  for  chromotropes. 

Newton's  disc,  as  it  is  called,  consists  of  all  the  colours 
of  the  spectrum,  painted  in  transparent  colours,  in  their 
right  proportions,  upon  a  revolving  disc,  and  as  this 
disc  is  rapidly  turned  in  the  lantern,  the  various 
colours  projected  upon  the  screen  in  front  mingle  together 
on  the  retina,  and  the  general  effect  is  that  of  white 
light.  It  may  happen  that  a  lecturer  may  touch 
upon  the  study  of  spectra  without  wishing  to  burden  him- 


186 


THE  BOOK  OF  THE  LANTERN. 


solf  with  the  necessary  apparatus  for  showing  them  upon 
the  screen.  Or  he  may  be  employing  a  large  lantern  to 
illustrate  other  parts  of  his  lecture,  which  would  be  quite 
unsuitable, — or,  at  any  rate,  would  have  to  be  re-arranged 
'  before  a  single  spectrum  experiment  could  be  shown. 
Feeling  this  want  myself,  I  devised  a  plan  for  showing- 
spectra  diagramatically  with  an  ordinary  biunial  lantern. 
(It  will  presently  be  seen  that  a  double  lantern  is  a  neces- 
sity for  this  particular  manner  of  working),  and  I  have 
found  the  method  adopted  to  answer  admirably.  A  special 
set  of  slides  is  required,  but  these  are  not  at  all  difficult 
to  make.  They  must  be  home-made,  for  they  are  not  to 
be  bought  at  present,  although  one  well-known  optician 
was  so  pleased  with  the  idea  when  I  described  it  to  him, 
that  he  expressed  his  intention  of  manufacturing  slides  of 
my  pattern.  The  first  of  the  set  is  a  photographic  slide 
showing  Newton's  well-known  experiment  with  a  prism, 
traversed  by  a  beam  of  light  admitted  through  an  aperture 
in  the  shutter  of  a  darkened  room.  The  next  slide  is  a 
simple-coloured  band,  or  continuous  spectrum.  This  is  at 
length  replaced  by  a  similar  band,  no  longer  continuous,  but 
crossed  by  the  principal  Frauenhofer  lines,  which  are  duly 
marked  above  with  their  own  distinguishing  letters.  Such 
a  spectrum  can  be  copied  from  any  work  on  optics,  and 
drawn  and  coloured  on  ground-glass,  as  explained  in 
another  part  of  this  book.  We  must  now  prepare  a  set  of 
slides  to  serve  as  "  effects "  for  this  last  spectrum  slide, 
and  which  will  consist  of  simple  bright  lines.  The  most 
simple  of  these  would  be  that  due  to  the  metal  sodium, 
which  would  consist  of  a  double  yellow  line,  to  agree  in 


THE  BOOK  OT  THB  LANTERN. 


187 


position  with  that  marked  D  in  the  spectrum -slide.  To 
produce  such  a  slide  it  is  only  necessary  to  paste  over  a 
piece  of  glass  a  piece  of  stout  black  paper,  and  to  cut 
out  with  a  sharp  knife,  when  the  paper  is  dry,  the  line 
required.  A  little  varnish  colour  over  the  cut-out  place  will 
complete  the  slide.  In  using  this  "  effect 99  the  audience 
should  have  explained  to  them  the  theory  which  seeks  to 
explain  the  reversal  of  the  lines  in  the  spectrum,  and  at 
the  right  moment  the  spectrum-slide  is  so  far  darkened 
by  moving  the  lantern-dissolver,  that  the  clear  sodium 
line  shines  out  brightly  over  the  spot  occupied  before  by 
the  dark  D  line.  I  need  hardly  say  that  the  two  slides 
must  be  in  perfect  register,  or  the  effect  will  be  spoiled. 
The  spectrum-slide  can  now  be  once  more  exhibited,  and 
another  bright  line  example  placed  in  the  other  lantern 
ready  to  be  made  visible  as  the  sodium  one  was  just 
now.  The  spectra  of  all  the  different  metals  can  thus  be 
illustrated  by  the  bright  lines  which  they  afford.  The 
method  may  perhaps  be  considered  rough,  but  the  effect  is 
startling,  and  few  among  a  general  audience  are  able  at 
once  to  realise  how  it  is  done. 

Double  refraction  can  be  shown  on  the  screen  in  the 
following  manner  :  A  card  with  a  simple  perforation  about 
one-eighth  of  an  inch  in  diameter  is  inserted  on  the  lantern- 
stage,  and  its  image  is  focussed  on  the  screen.  A  crystal 
of  Iceland  spa  is  then  placed  between  this  card  and  the 
objective  lens,  and  two  spots  of  light  will  become  apparent 
upon  the  sheet. 

It  may  be  mentioned  here  that  in  all  experiments  where 
colour  is  required  it  is  better,  if  possible,  to  use  coloured 


188 


THE  BOOK  OF  THE  LANTERN. 


gelatine  than  any  other  medium.  Ordinary  coloured  glass 
absorbs  so  much  light  that  it  is  of  very  little  use  in  lantern 
experiments  ;  and  if  the  operator  will  try  the  effect  of 
coloured  glass  and  coloured  gelatine  side  by  side  he  will 
be  surprised  at  the  advantage  gained  from  using  the  latter. 
There  is  one  objection  to  gelatine,  and  that  is,  if  a  very 
powerful  limelight  be  used  it  is  apt  to  be  affected  by  the 
heat ;  but  this  is  only  the  case  if  the  medium  in  question 
is  kept  for  a  protracted  time  on  the  lantern-stage. 

A  large  number  of  experiments  illustrating  the  theory 
of  colour  and  the  laws  of  complimentary  tints  can  be 
arranged  by  means  of  pieces  of  cardboard  with  different 
shaped  orifices  cut  in  them,  filled  in  with  coloured  gelatine. 
Such  examples  will  easily  suggest  themselves  to  any 
operator  with  the  assistance  of  a  reliable  book  on  the 
theory  of  colour.  I  may  mention  here  a  simple  arrange- 
ment for  showing  the  way  in  which  the  retina  becomes 
fatigued  by  looking  at  an  object  for  some  time. 

It  consists  of  a  card  with 
two   semicircular  openings, 
n   divided  by  a  horizontal  bar 
|   (see  fig.  49).  Over  one  open- 
•  ing,  say  the  lower   one,  a 
Fig.  49.  piece  of  card  is  placed  so 

that  the  image  of  the  upper  one  alone  is  projected  upon 
the  screen.  After  looking  at  this  image  for  some  time, 
the  card  obscuring  the  lower  opening  is  suddenly  with- 
drawn, and  it  is  then  strange  to  note  how  one  opening 
appears  to  be  far  duller  than  the  other,  although  both  are 
in  reality  equally  illuminated. 


THE  BOOK  OF  THE  LANTERN. 


189 


Another  method  which  illustrates  the  tiring  of  the 
retina,  and  which  also  demonstrates  the  law  of  compli- 
mentary colours,  can  be  shown  thus  : — 

A  card  having  a  round  opening  in  the  centre,  filled  in 
with  red  gelatine,  is  placed  on  the  lantern  stage,  and  its 
image  allowed  to  remain  upon  the  sheet  for  some  little 
time,  the  attention  of  the  spectator  being  concentrated 
upon  it.  Thd  gelatine  is  suddenly  removed,  when  al- 
though the  image  of  the  opening  is  of  course  perfectly 
white,  it  appears  to  be  green,  because  the  retina  is  tired 
by  its  exposure  to  the  red,  and  can  only  for  a  time  appre- 
ciate the  remaining  colours  of  the  spectrum,  which  mingled 
form  green;  of  course,  any  primary  colour  can  be  chosen 
for  the  experiment,  and  its  complementary  tint  will  be 
made  manifest.  This  is  but  a  variation  of  that  advertise- 
ment which  has  been  so  common  in  our  streets  for  some 
time,  where  the  onlooker  is  invited  to  gaze  upon  cer- 
tain colours  for  so  many  seconds,  when  the  image  of  the 
coloured  letters  looked  at  will  appear,  bi*t  in  their  com- 
plementary tint,  upon  the  blank  space  above. 

For  experimental  work  with  the  lantern,  a  special  form 
of  instrument  should  be  used.  I  have  lately  seen  a  form 
which  I  think  found  its  origin  in  Germany;  in  which  the 
objective  is  so  arranged  on  a  sliding  base  board,  that  a 
clear  space  of  some  inches  is  left  between  it  and  the  lantern 
condensers ;  while  a  little  table  between  the  two  serves  to 
support  any  object  whose  shadow  it  is  desirable  to  throw 
upon  the  screen.  If  we  are  content  with  the  mineral  oil 
lantern, — and  with  such  a  lantern  a  great  many  experiments 
can  be  shown,  at  any  rate  in  a  small  room, — rwe  can  ar- 


* 


190 


THE  BOOK  OP  THE  LANTERN. 


range  matters  in  a  very  simple  manner.  Let  the  lantern 
stand  on  a  base  board,  and  let  the  objective  be  supported 
upon  a  sliding  piece  in  front  of  that  board.  Cut  away  the 
tin  nozzle  upon  which  the  objective  fits  in  the  ordinary 
way,  so  that  any  object  can  easily  be  brought  between 
condenser  and  objective.  Or  to  still  more  simplify  the 
matter,  we  can  use  the  lamp  only  of  one  of  these  mineral 
lanterns  and  place  it  as  figured  in  the  annexed  cut  (fig.  50). 


Fig.  50. 


Here  we  have  a  base  board  AA,  with  a  fixed  support  in  the 
centre  B,  which  is  pierced  with  a  hole  sufficiently  large  to 
contain  the  condensers  of  the  lantern.  Close  up  to  this 
is  placed  the  lamp  L.  Another  support,  C,  holds  the  objec- 
tive, and  this  support  by  means  of  a  sliding  piece  let  into 
the  base  board,  can  be  moved  to  and  fro  for  focussing  pur- 
poses in  front  of  the  condensers.  It  will  be  seen  that  by 
adopting  this  arrangement,  no  lantern  is  necessary.  We 
simply  require  the  illuminator,  which  must  of  course  be 
closed  in,  as  sold  with  most  lanterns ;  a  condensing  lens  ; 
and  an  objective. 

The  number  of  beautiful  experiments  which  are  possible 
with  the  use  of  a  glass  tank,  or  rather,  several  glass  tanks 
of  the  simple  form  shown  in  fig.  51  are  surprising.  Most 


THE  BOOK  OP  THE  LANTERN", 


191 


of  these  are  of  a  chemical  nature,  but  there  aro  others 
which  exhibit  physical  phenomena  in  a  manner  which  is 
perhaps,  impossible  by  any  other  means,  or  rather,  we  may 
say,  that  experiments  which  can  only  under  normal  con- 
ditions be  viewed  by  one  or  two  pairs  of  eyes  on  the  lecture 
table,  can  by  means  of  this  tank  be  made  visible  to  a  large 
audience. 

A  fine  experiment  showing  the  formation  of  vortex 
rings  may  be  shown  in  the  following  way.  Having  filled 
the  tank  with  clean  water,  take  a  penholder  or  a  piece  of 
stick  pointed  for  the  purpose  and  dip  it  into  some  milk,  so 
that  a  drop  forms  at  the  end  of  it.  Bring  this  carefully  over 
the  tank  and  allow  the  milk  to  just  graze  the  surface  of 
the  water,  when  it  will  form  a  white  ring  in  the  fluid 
which  will  fall  gradually  downward,  but  on  the  screen, 
of  course,  it  will  appear  to  rise  upward.  This  ring  as  it 
travels  to  the  bottom  of  the  tank  will  give  rise  to  other 
similar  rings,  so  that  presently  there  will  be  quite  a  number 
of  circles  slowly  moving  upwards  on  the  screen.  This* 
experiment  is  one  which  will  illustrate  well  the  formation 
of  smoke  rings,  and  of  the  more  important  phenomena  of 
whirlpools  and  whirlwinds. 

Another  experiment  of  a  similar  nature,  and  giving  a  fine 
effect  on  the  screen,  may  be  performed  by  filling  the  tank 
to  within  half  an  inch  of  the  top  with  methylated  spirit. 
Take  now  instead  of  a  wooden  rod  one  of  glass,  or  a  camel 
hair  brush  will  do  as  well.  Dip  it  into  an  alcoholic  solution 
of  any  of  the  aniline  dyes,  and  just  allow  the  drop  which 
hangs  from  it  to  touch  the  inner  side  of  one  of  the  glasses 
of  the  tank.    Directly  this  drop  reaches  the  alcohol,  it  will 


192 


THE  BOOK  OF  THE  LANTERN. 


descend  and  immediately  break  out  into  a  number  of 
branches.  These  branches  will  on  the  screen  appear  to  rise 
rapidly  upwards  after  the  manner  of  a  number  of  coloured 
rockets,  and  by  varying  the  colours  of  the  dyes  and  putting 
one  or  two  drops  into  the  tank  simultaneously,  a  most  lovely 
effect  on  the  screen  is  obtained. 

The  decomposition  of  water  is  another  experiment  which 
has  a  most  curious  effect.  For  this  experiment  a  small  electric 
battery  is  necessary,  and  the  most  convenient  form  to  use  is 
a  single  bichromate  cell,  say  of  one  pint  capacity.  This  can 
be  hidden  away  in  a  box  beneath  the  lantern,  and  as  it 
gives  off  no  fumes,  there  is  nothing  disagreeable  in  its  use  ; 
moreover  its  action,  if  freshly  charged,  is  energetic,  and  this 
action  can  be  stopped  when  required  by  lifting  the  zinc 
plate  from  the  solution  in  which  it  is  immersed.  The  wires 
from  the  poles  of  the  battery  must  be  long  enough  to  reach 
the  lantern  stage  ;  the  slide  for  this  experiment  being  simple 
in  the  extreme.  The  tank  to  be  used  should  be  of  rectangular 
•form,  and  as  a  matter  of  convenience,  it  should  be  furnished 
with  two  binding  screws  on  one  of  its  outer  sides,  so  that 
the  wires  from  the  battery  can  be  readily  connected  with 
them.  These  screws  should  be  in  connection  with  two 
gutta-percha  covered  wires,  which  proceed  to  the  bottom  of 
the  tank,  where  their  ends  are  bare  and  turned  upwards  for 
about  a  quarter  of  an  inch.  These  ends  may  be  so  fixed 
that  they  are  about  half  an  inch  apart.  The  tank  is  pre- 
viously filled  with  diluted  sulphuric  acid  (one  part  of  acid 
to  eight  of  water),  and  is  then  ready  for  action.  Directly 
connection  is  made  with  the  battery,  the  two  wires  will 
rapidly  give  off  bubbles  of  gas,  one  being  hydrogen  and 


THE  BOOK  OF  THE  LANTERN. 


193 


the  other  oxygen.  It  is  possible  to  elaborate  this  slide  by 
crowning  the  two  terminals  with  tiny  inverted  test  tnbes, 
filled  with  the  acidulated  liquid.  In  this  case  the  bubbles 
of  gas  displace  the  contained  water  in  the  tubes,  the  hydro- 
gen tube  being  readily  distinguished  by  being  emptied  of 
water  at  double  the  rate  of  the  tube  devoted  to  the  oxygen 
gas.  This  proves  in  a  very  direct  manner  the  composition 
of  water,  which  consists  of  two  volumes  of  hydrogen  to 
one  of  oxygen. 

In  order  to  show  the  generation  of  hydrogen  gas  alone,  a 
still  more  simple  arrangement  can  be  adopted.  The  electric 
battery  is  not  used  for  this  experiment.  A  few  pieces  of 
granulated  zinc  are  dropped  into  the  tank  of  acid  water, 
when  bubbles  of  hydrogen  will  be  rapidly  given  off,  their 
downward  descent  upon  the  screen  giving  a  very  peculiar 
effect. 

In  like  manner  carbonic  acid  gas  can  be  generated  by 
using  a  few  pieces  of  marble  instead  of  the  zinc,  aud  sub- 
stituting for  the  sulphuric  acid  water  which  has  been  acidu- 
lated with  hydrochloric  acid.  We  can  also  easily  show 
that  one  of  the  products  of  the  lungs  is  this  same  carbonic 
acid  gas.  In  this  case  the  tank  must  be  filled  with  lime 
water,  which  will  remain  perfectly  clear  until  it  is  blown  into 
from  the  lungs  by  means  of  a  tiny  glass  tube,  when  bubbles 
of  air  will  rise  from  the  water,  and  the  liquid  will  rapidly 
become  cloudy,  proving  that  the  carbonic  acid  from  the 
lungs  has  formed  carbonate  of  lime,  or  common  chalk,  in 
the  water. 

It  will  be  noticed  that  in  all  tank  experiments  it  is 
necessary  that  the  lantern  stage  should  be  open  at  the  top 

o 


194 


THE  BOOK  OF  THE  LANTERN. 


and  such  experiments  are  for  this  reason  best  performed 
with  a  lantern  having  the  simple  construction  shown  in 
Fig.  49.  These  experiments  are  so  valuable  for  educa- 
tional purposes,  and  can  so  easily  be  shown  with  ordinary 
oil-lit  lanterns  that  it  is  to  be  hoped  that  manufacturers 
will  see  the  necessity  of  providing  for  them  by  the  adop- 
tion of  an  open  stage. 

The  composition  of  Prussian  blue  can  be  easily  demon- 
strated by  means  of  the  chemical  tank.  For  this  experiment 
we  shall  require  a  solution  of  the  yellow  prussiate  of 
potash  from  which  the  colour  takes  its  name.  This  is 
placed  in  the  tank.  Have  in  readiness  a  solution  of  sul- 
phate of  iron  or  green  vitriol.  On  pouring  the  contents 
of  this  bottle  by  means  of  a  pipette  into  the  tank,  a  heavy 
blue  precipitate  is  thrown  down,  but  as  this  precipitate  is 
opaque  the  colour  is  not  perceptible  on  the  screen ;  but  by 
adding  to  the  blue  precipitate  a  few  drops  of  sulphuric 
acid,  and  following  this  by  a  little  bi-chromate  of  potash 
in  solution,  a  brilliant  transparent  blue  is  immediately 
made  apparent.  The  formation  of  other  colours  can  by 
reference  to  any  book  on  chemistry  be  readily  demon- 
strated. 

The  tests  for  acid  and  alkaline  solutions  by  means  of 
litmus  can  be  demonstrated  in  the  following  way  : — 

Fill  the  tank  with  a  solution  of  litmus  or  with  an  in- 
fusion of  purple  cabbage,  made  by  slicing  a  few  of  the 
leaves,  and  pouring  boiling  water  upon  them.  Place  either 
of  these  solutions  in  the  tank,  when,  upon  adding  a  small 
quantity  of  acid,  the  liquid  will  be  seen  to  turn  red ;  sub- 
sequent addition  of  an  alkali,  such  as  a  weak  solution  of 


THE  BOOK  OF  THE  LANTERN. 


195 


ammonia,  will  quickly  restore  the  original  colonr,  and  these 
changes  from  red  to  blue,  and  vice  versa,  can  be  continued 
by  adding  acid  and  alkali  alternately,  as  often  as  may  be 
required. 

If  the  tank  be  charged  with  a  solution  of  sulphate  of 
iron  and  gallic  acid  be  added  to  it,  a  black  solution  of  ink 
will  immediately  be  produced.  Another  pretty  experiment 
demonstrates  the  presence  in  hard  water  of  various  mineral 
matters  which  will  cause  certain  chemicals  to  give  a 
precipitate  which  they  would  not  do  in  water  that  has 
been  freed  from  mineral  matter  by  distillation.  A  good 
plan  of  showing  this  is  to  suspend  in  a  tank  a  crystal  of 
oxalic  acid.  As  the  crystal  dissolves  in  the  water  long 
threads  of  oxalate  of  lime  will  be  given  off  by  it,  forming 
a  very  curious  appearance  on  the  screen.  It  may  then  be 
shown  that  by  the  substitution  of  distilled  for  hard  water 
the  crystal  will  dissolve  all  the  same,  but  these  threads  will 
not  be  given  off,  because  there  is  no  lime  present  to  form 
them.  The  action  of  bleaching  powder,  commonly  called 
chloride  of  lime,  is  well  shown  by  filling  the  tank  with  a 
solution  of  indigo,  which  has  been  acidified  with  sulphuric 
acid.  Upon  adding  a  solution  of  the  bleaching  powder, 
the  sulphuric  acid  will  liberate  the  chlorine  contained  in 
it,  and  will  discharge  the  blue  colour  of  the  indigo,  leaving 
the  disc  on  the  screen  perfectly  white. 

The  precipitates  caused  by  the  admixture  of  various 
chemicals  is  not  effective  in  the  lantern,  for  the  reason  that 
most  of  these  precipitates  are  opaque,  and  therefore  they 
look  black  upon  the  screen. 

For  instance,  we  may  fill  a  tank  with  a  solution  of 

o2 


196 


THE  BOOK  OF  THE  LANTERN, 


common  salt, — i.e.,  the  chloride  of  sodium,  — and  upon  adding 
to  this  a  small  quantity  of  nitrate  of  silver  in  solution,  a 
heavy  white  precipitate  of  chloride  of  silver  is  thrown 
down,  but  as  this  is  perfectly  opaque  it  will  only  appear  on 
the  screen  as  black  clouds. 

Other  very  beautiful  experiments  may  be  performed  to 
demonstrate  the  crystallisation  of  various  salts.  Plates  of 
glass  may  be  prepared  beforehand  with  saturated  solutions 
of  the  salts,  and  these  plates,  slipped  into  a  slide  carrier, 
can  be  used  for  projection,  giving  very  fine  effects.  But 
by  far  the  most  striking  way  of  exhibiting  these  interesting 
phenomena  is  to  show  the  crystallisation  actually  in 
progress. 

This  is  easy  enough  if  the  lantern  be  furnished  with  a 
vertical  attachment,  but  not  so  easy  without  such  an 
appendage.  But  the  following  experiments  can  be  readily 
performed  with  an  ordinary  lantern.  Prepare  a  saturated 
solution  of  sal-ammoniac,  and  with  the  help  of  a  camel-hair 
brush  cover  a  clean  glass  plate  with  the  liquid ;  place  this 
glass  on  the  lantern  stage,  when  the  heat  from  the  lamp 
will  speedily  cause  the  water  to  evaporate  and  the  crystals 
to  form  on  the  glass.  It  will  be  noticed  that  in  the  crys- 
tallisation of  this  salt  the  branches  of  the  marvellous  tree, 
which  grows  so  rapidly  on  the  screen,  always  keep  at  a 
particular  angle  to  its  stem.  Another  experiment  of  a  like 
nature  is  performed  by  employing  a  solution  of  urea  in 
alcohol,  in  which  the  crystallisation  is  quite  different,  the 
plate  being  quickly  covered  with  bundles  of  fibres  which 
are  no  longer  at  right  angles  to  the  stem  from  which 
they  spring,  but  take  ail  kinds  of  different  directions. 


THE  BOOK  OF  THE  LANTERN. 


197 


These  experiments  are  of  great  use  in  demonstrating 
the  gradual  crystallisation  of  the  various  mineral  sub- 
stances of  which  the  crust  of  the  earth  is  composed.  A 
yery  beautiful  experiment,  showing  the  structure  of  ice, 
has  been  devised  by  Professor  Tyndall.  I  cannot  do 
better  than  describe  the  manner  of  performing  it  in  his 
own  words  :  "  Take  a  slab  of  lake  ice  and  place  it  in  the 
path  of  a  concentrated  sunbeam.  Watch  the  track  of  the 
beam  through  the  ice.  Part  of  the  beam  is  stopped,  part 
of  it  goes  through ;  the  former  produces  internal  lique- 
faction, the  latter  has  no  effect  whatever  upon  the  ice. 
Bat  the  liquefaction  is  not  uniformly  diffused.  From 
separate  spots  of  the  ice  little  shining  points  are  seen  to 
sparkle  forth.  Every  one  of  those  points  is  surrounded  by 
a  beautiful  liquid  flower  with  six  petals. 

"  Ice  and  water  are  so  optically  alike  that  unless  the  light 
fall  properly  upon  these  flowers,  you  cannot  see  them. 
But  what  is  the  central  spot  ?  A  vacuum.  Ice  swims  on 
water  because,  bulk  for  bulk,  it  is  lighter  than  water ;  so 
that  when  ice  is  melted  it  shrinks  in  size.  Can  the  liquid 
flowers  then  occupy  the  whole  space  of  the  ice  melted  ? 
Plainly  no.  A  little  empty  space  is  formed  with  the 
flowers,  and  this  space,  or  rather  its  surface,  shines  in  the 
sun  with  the  lustre  of  burnished  silver. 

"  In  all  cases  the  flowers  are  formed  parallel  to  the  sur- 
face of  freezing.  They  are  formed  when  the  sun  shines 
upon  the  ice  of  every  lake;  sometimes  in  myriads,  and  so 
small  as  to  require  a  magnifying  glass  to  see  them.  They 
are  always  attainable,  but  their  beauty  is  often  marred  by 
internal  defects  of  the  ice.    Even  one  portion,  of  the  same 


198 


THE  BOOK  OF  THE  LANTERN. 


piece  of  ice  may  show  them  exquisitely,  while  a  second 
portion  shows  them  imperfectly. 

"  Here  we  have  a  reversal  of  the  process  of  crystallisation. 
The  searching  solar  beam  is  delicate  enough  to  take  the 
molecules  down  without  deranging  the  order  of  their  archi- 
tecture. Try  the  experiment  for  yourself  with  a  pocket- 
lens  on  a  sunny  day.  You  will  not  find  the  flowers  con- 
fused ;  they  all  lie  parallel  to  the  surface  of  freezing.  In 
this  exquisite  way  every  bit  of  the  ice  over  which  our 
skaters  glide  in  winter  is  put  together." 

One  of  the  most  interesting  chemical  operations  to 
witness  is  the  development  of  a  photograph, — and  even 
experienced  workers  will  say  that  they  never  tire  of 
watching  the  gradual  unfolding  of  the  wonderful  image. 
Those  who  have  never  before  had  the  opportunity  of  watching 
the  effect  of  the  developing  fluid  on  the  blank  plate,  are 
delighted  when  first  the  operation  is  brought  under  their 
notice.  It  is  certainly  an  experiment  which  never  fails  to 
interest  an  audience,  when  properly  performed,  as  it  can  be, 
in  the  optical  lantern.  But  the  operator  must  not  be 
a  novice  in  photography,  or  he  will  probably  fail,  for  the 
experiment  requires  experience,  and  great  care  in  all 
its  stages. 

A  gelatine  bromide  plate,  such  as  is  ordinarily  used 
for  negative  work,  is  of  no  use  whatever  here,  for  the 
film  is  too  opaque  for  the  purpose.  A  gelatine  chloride  plate 
(such  as  that  described  on  page  133)  is  the  right  thing  to 
employ.  If  we  compare  a  bromide  and  a  chloride  plate  side 
by  side  in  the  dark  room,  we  shall  soon  see  that  there  is 
little  difficulty  in  distinguishing  the  one  from  the  other.  In 


THE  BOOK  OF  THE  LANTERN. 


199 


the  first  case,  the  film  is  so  thick  that  we  can  see  nothing 
throngh  it,  but  in  the  case  of  the  chloride  plate  the  flame  of 
the  red  lamp  can  easily  be  seen  through  the  glass ;  indeed, 
upon  first  using  such  plates,  photographers  are  apt  to 
wonder  whether  so  thin  a  film  can  ever  yield  a  picture.  As 
a  matter  of  fact,  the  film  is  as  thick  as  that  upon  a  bromide 
plate,  only  the  emulsion  of  which  it  is  composed  is  of  a 
far  more  transparent  quality. 

Having  then  a  chloride  plate  at  hand,  and  having  if  ne- 
cessary cut  it  down  to  a  size  which  will  enable  it  to  slip 
with  ease  into  a  chemical  tank,  the  course  of  operations 
will  be  as  follows: — 1,  Exposure;  2,  development;  and 
3 j  fixation. 

Provide  a  good  negative  (if  it  be  a  portrait  of  some  one  . 
well  known  to  the  spectators,  so  much  the  better),  and  place 
it  in  a  printing  frame,  with  the  chloride  plate  against  it, 
film  to  film.  Expose  to  the  light  of  an  inch  of  magnesium 
wire  held  two  feet  away  from  the  printing  frame,  or  to  the 
rays  of  the  lime  light  for  about  ten  seconds.  Now  place 
the  little  tank  on  the  stage  of  the  lantern,  and  against  the 
inner  side  of  it,  that  is,  next  the  light  place  a  sheet 
of  ruby  glass.  The  effect  upon  the  screen  will  now  be 
simply  that  of  a  blank  red  disc.  The  exposed  plate  may 
now  be  taken  from  the  printing  frame  and  placed  in  the 
tank.  Take  good  care  that  it  is  placed  there  upside  down, 
so  that  the  image  when  developed  will  appear  the  right  way 
up.  The  developing  fluid,  ferrous  oxalate  (see  page  121), 
may  now  be  mixed.  This  should  be  at  hand  in  two  solu- 
tions, so  that  by  mixing  the  one  with  the  other  the  de- 
veloper is  ready  without  any  delay.    As  it  is  poured  into 


200 


THE  BOOK  OF  THE  LANTERN. 


the  tank,  the  surface  of  the  fluid  will  appear  as  a  descending 
line  across  the  sheet.  The  strength  of  the  developer  should 
not  be  so  great  as  for  ordinary  development,  by  which  I 
mean  that  the  proportion  of  iron  can  be  conveniently 
reduced  so  as  to  render  development  less  sudden  than  it 
generally  is  with  chloride  plates.  When  once  the  developer 
has  been  poured  into  the  tank,  the  red  glass  can  be  with- 
drawn, for  the  ferrous  oxalate  developer  is  red  enough  in 
itself  to  form  a  protection  to  the  plate  from  the  light. 
Presently  the  image  will  begin  to  appear,  and  will  gradually 
gain  in  strength.  When  it  is  fully  developed,  as  it  will  be 
in  about  two  minutes,  the  plate  can  be  removed,  washed, 
and  placed  once  more  in  the  lantern  in  a  tank  of  fixing  solu- 
tion. Here  it  will  gradually  get  clear,  as  the  unaltered 
chloride  is  acted  upon  by  the  hyposulphite  of  soda  solution. 

To  perform  this  interesting  experiment  in  the  most  per- 
fect manner,  a  special  form  of  tank  may  be  employed.  It 
should  have  a  tap  at  its  lower  part,  to  act  as  a  waste  pipe. 
With  this  arrangement  the  chloride  plate  need  not  be 
removed  from  the  tank  at  any  stage  of  the  process.  When 
development  is  complete,  the  ferrous  oxalate  can  be  drawn 
off ;  then  water  can  be  poured  in,  to  be  immediately  drawn 
off  and  replaced  by  the  hypo  solution. 

The  chloride  plate  employed  can  be  put  into  the  printing 
frame  by  gaslight,  provided  that  the  operation  be  performed 
with  ordinary  despatch.  It  should  be  noted,  too,  that  these 
plates,  or  at  least  some  brands  of  them,  rapidly  deteriorate. 
But  the  careful  operator  will  try  the  experiment  in  private 
before  he  ventures  before  the  public,  and  will  take  care  that 
his  plates  are  above  suspicion. 


THE  BOOK  OF  THE  LANTERN. 


201 


Magnetic  experiments  are  always  attractive,  and  can  be 
well  shown  with  the  lantern,  for  they  gain  greatly  by  the 
magnification  possible  with  that  instrument.  Fig.  52  shows 
a  simple  form  of  slide  which  can  be  manufactured  without 
much  trouble ;  it  consists  of  a  bar  of  soft  iron,  bent  as 
shown,  and  pointed  at  its  ends.  These  ends  or  poles  are 
brought  to  within  half  an  inch  of  each  other.  Two 
wooden  or  cardboard  reels,  wound  with  a  quantity  of  silk 
covered  copper  wire,  complete  the  arrangement.  The 
battery  already  recommended  can  be  used  with  this  mag- 
netic slide.    Here  are  a  few  experiments  possible  with  the 


Fig.  52. 

contrivance.  Drop  upon  the  poles  some  iron  filings,  and 
show  that  they  are  not  attracted  until  the  battery  connec- 
tion is  made,  for  then  and  only  then  has  the  iron  magnetic 
properties  conferred  upon  it.  Drop  a  number  of  small 
French  nails,  technically  known  as  pins,  upon  the  poles, 
when  they  will  meet  and  assume  curious  forms,  until  the 
current  is  broken,  when  they  will  fall  upward,  as  it  will 
appear.  A  tiny  disc  of  iron  attached  to  the  end  of  a  silk 
thread  and  hung  between  the  poles  will  take  up  a  rigid 
position  directly  the  battery  connection  is  made,  a  similar 


202 


THE  BOOK  OF  THE  LANTERN. 


one  of  bismuth  assuming  the  opposite  direction  under  the 
same  conditions.  This  last  experiment  is  to  show  the 
difference  between  a  magnetic  and  dia-magnetic  body. 

But  the  most  beautiful  magnetic  experiments  are  only- 
possible  with  a  vertical  attachment  fitted  to  the  lantern. 
Obtain  a  couple  of  flat  bar  magnets  two  inches  in  length. 
Place  one  of  these  in  the  centre  of  the  horizontal  stage,  and 
focus  sharply  on  the  screen.  The  appearance  is  that  of  a 
thick  black  bar.  "Now  sift  through  a  muslin  bag  some  iron 
filings,  so  that  the  screen  appears  covered  with  black  spots. 
Tap  the  stage  with  the  finger  nail,  so  as  to  disturb  the 
particles  of  iron,  and  they  will  be  seen  to  gather  round  the 
poles  of  the  little  magnet,  and  to  form  the  beautiful  magnetic 
curves.  A  still  more  striking  experiment  may  be  per- 
formed with  two  magnets  so  placed  that  their  poles  of 
opposite  names, — N".  and  S., — face  one  another,  while  they 
are  at  the  same  time  about  one  inch  apart.  Now  scatter 
the  filings  as  before,  and  the  effect  of  the  graceful  curves 
embracing  one  another  between  the  two  poles  is  simply 
magnificent.  Remove  the  magnets,  wipe  the  filings  from 
the  stage,  and  once  more  arrange  the  bars  in  the  same 
position,  but  with  poles  of  the  same  name  facing  one 
another.  When  the  filings  are  now  scattered  over  the 
magnets,  a  great  contrast  to  the  last  experiment  is  apparent. 
Where  just  now  all  was  harmony,  there  is  visible  antago- 
nism. "  Poles  of  opposite  name  attract  one  another,  and  of 
the  same  name  repel  one  another."  And  this  repulsion  is 
most  beautifully  shown.  The  curves  no  longer  embrace 
one  another,  but  meet  and  turn  back  upon  themselves, 
forming  a  line  of  confusion  where  the  meeting  takes 


THE  BOOK  OF  THE  LANTERN. 


203 


place.  The  experiments  can  be  varied  by  altering  the 
position  of  the  magnets,  or  by  nsing  knitting  needles  which 
have  been  jnst  before  magnetised  at  the  lecture  table.  It 
will  be  noticed  that  these  curve  experiments  require  no 
battery  power.  They  are  performed  with  what  are  known 
as  permanent  magnets,  in  contradistinction  to  the  electro 
magnet  used  with  the  special  form  of  slide  shown  at 
fig.  52. 

In  describing  some  of  the  experiments  possible  with  the 
optical  lantern,  I  have  purposely  refrained  from  detailing 
any  of  the  splendid  effects  due  to  polarised  light — for  these 
have  been  already  dealt  with  by  my  friend  Mr.  Lewis 
Wright,  in  a  manner  which  it  would  be  impossible  to 
improve  upon.1 

1  "  Light :  a  Course  of  Experimental  Optics,  chiefly  with  the 
Lantern.' '    Macmillan  &  Co. 


CHAPTER  XIY. 


THE  LANTERN  AS  AN  AID  TO  PHOTOGRAPHY. 

HEN  a  photographic  aspirant  first  enters  npon  the 
practice  of  what  nsed  to  be  known  as  the  "  black 
art,"  bnt  which  now,  thanks  to  the  cleanliness  of 
dry  plate  work,  no  longer  merits  that  stigma,  his  friends 
and  relatives  all  look  anxiously  for  some  tangible  results 
from  his  mysterious  operations.  To  them  a  negative, 
albeit  it  may  show  lovely  gradations  of  tone,  and 
beauties  of  detail,  which  a  master's  eye  would  revel 
in,  is  negative  in  a  far  wider  sense  than  its  producer 
would  be  inclined  to  allow.  A  production  in  which 
bright  skies  and  white  skins  are  black  as  night,  is  a 
thing  which  cannot  be  understood  or  tolerated,  and  until  a 
print  of  that  negative  is  produced, — and  sometimes  alas  ! 
even  then, — the  domestic  critics  are  inclined  to  consider  the 
amateur  worker  a  fraud.  The  painstaking  photographer, 
after  he  has  succeeded  in  obtaining  a  few  negatives,  will  be 
anxious  on  this  account,  if  not  for  his  own  satisfaction,  to 
print  some  positives  from  them.    These  will  afterwards  be 


TITE  BOOK  OP  THE  LANTERN. 


205 


mounted  in  an  album,  and  much  pleasure  will  doubtless  be 
derived  from  them.  They  may  possibly  not  be  grand 
specimens  of  solar  work,  but  they  will  serve  to  remind  the 
author  of  many  a  pleasant  ramble,  and  many  little  incidents 
of  places  visited  and  people  met  with,  which  otherwise 
might  have  passed  into  oblivion.  He  will  be  able  "  to  fight 
his  battles  o'er  again/'  as  he  tells  his  friends  of  difficulties 
encountered  by  the  way.  But  at  the  best  this  means  a 
great  deal  of  work,  and.  work,  too,  which  to  a  great  extent 
is  mechanical,  and  therefore  tedious.  The  printing,  toning 
and  fixing  of  a  batch  of  prints  is  no  light  matter  to  an  ama- 
teur, who  has  generally  to  do  everything  for  himself.  Some 
prints  are  sure  to  get  over-exposed,  others  suffer  from  the 
opposite  failing,  and  even  if  all  goes  well  in  the  preliminary 
operation  of  exposure,  there  is  that  terrible  toning  bath  to 
come.  This  bath  sometimes,  for  some  obscure  reason,  will 
refuse  to  give  the  desired  colour,  and  our  batch  of  prints, 
instead  of  being  "  joys  for  ever,"  turn  out  to  be  sandy- 
looking,  bilious  objects,  which  we  are  afraid  to  show  to 
anybody. 

What  if  some  magician  were  to  appear  suddenly  at  the 
elbow  of  the  disgusted  worker,  and  tell  him  that  there  was 
a  way  of  producing  positives  from  those  negatives  without 
all  this  trouble  ?  That  such  positives  could  be  shown  en- 
larged to  an  almost  indefinite  extent,  and  that  pictures  five, 
ten,  or  fifteen  feet  in  diameter  could  be  shown  in  perfection, 
the  original  negative  from  which  they  are  taken  measuring 
only  three  and  a  quarter  inches.  There  is  no  need  for  any 
magician,  for  the  thing  can  be  achieved,  not  easily,  for  the 
work,  like  most  photographic  manipulations,  requires  a 


20G  THE  BOOK  OF  THE  LANTERN. 

great  deal  of  patience  and  practice  before  success  is 
attained.  The  requisites  are  good  photographic  transpa- 
rencies on  glass,  and  a  good  optical  lantern  wherewith  to 
exhibit  them. 

The  lantern  method  of  showing  photographs  has  the  ob- 
vious advantage  that  a  large  number  can  at  the  same  time 
view  the  same  picture  under  the  best  conditions.  They  can 
exchange  opinions  as  to  its  merits,  and  can  point  out  little 
bits  of  detail  which  would  be  almost  invisible  in  a  paper 
print  from  the  original  small  negative.    A  great  many 
amateurs,  too,  take  only  small  negatives.    They  do  not  care 
to  be  burdened  in  their  rambles  with  a  large  camera, 
which,  with  its  inevitable  dark  slides  or  changing  box, 
forms  a  very  heavy  travelling  companion.    Many,  there- 
fore, are  wise  enough  to  content  themselves  with  either  a 
quarter-plate  apparatus,  or  one  which  gives  pictures  mea- 
suring 5  by  4  inches.    Prints  from  these  small  negatives 
are  rather  insignificant  when  mounted  in  an  album,  but 
such  negatives  are  just  what  are  required  for  lantern  trans- 
parency making  ;  so  that  the  tourist  with  his  little  camera 
is,  with  the  help  of  the  lantern,  placed  on  the  same  footing 
as  the  toiler  with  large  and  heavy  apparatus.    He  can  in- 
crease the  size  of  his  pictures,  or  rather  the  images  of  such 
pictures,  to  any  reasonable  extent.    I  know  of  an  amateur 
photographer  who  spent  three  months  on  a  Mediterranean 
tour.    He  took  with  him  a  quarter-plate  camera,  and  its 
accessories,  together  with  a  stock  of  gelatine  plates.  He 
brought  back  with  him  about  one  hundred  and  fifty  capital 
negatives,  which  were  taken  in  Algeria,  Tunis,  Malta, 
Sicily,  and  Southern  Italy.    On  his  arrival  in  England 


THE  BOOK  OF  THE  LANTERN. 


207 


these  were  all  printed  as  lantern  transparencies,  and  he  is 
now  able  to  entertain  his  friends  with  an  acconnt  of  his 
wanderings,  and  to  illustrate  his  remarks  in  a  very  pleasant 
and  novel  manner.  If  the  same  negatives  had  been  merely 
printed  on  paper  in  the  usual  manner,  and  shown  in  an 
album,  they  would,  by  reason  of  their  smallness,  have  met 
with  but  scant  appreciation. 

I  may  instance  another  way  in  which  the  lantern  can  be 
utilised  without  the  necessity  of  taking  original  negatives. 
Most  travellers  abroad  collect  photographs  of  any  place  they 
may  visit,  and  an  enormous  trade  is  now  done  in  such 
pictures.  These  are  brought  home  in  due  course,  mounted 
in  an  album,  and  too  often,  alas  !  gradually  fade  into  sickly 
yellow  ghosts  of  their  former  selves.  Now,  if  these  pictures 
were  copied  by  a  small  quarter-plate  camera,  the  negatives 
thus  obtained  could  in  their  turn  furnish  positives  on  glass 
for  use  in  the  lantern.  Transparencies  so  produced  are 
never,  it  is  true,  so  good  as  those  from  original  negatives, 
for  the  texture  and  the  gloss  of  the  paper  prints  will  gene- 
rally to  some  extent  show  themselves  in  the  reproduced 
negative,  but  still  it  is  wonderful  what  good  results  can  be 
obtained  in  this  way.  Indeed,  I  may  say  that  it  requires  a 
critical  eye  to  detect  that  a  second  negative  has  been  em- 
ployed. I  have  already  detailed  the  best  method  of  pro- 
ducing these  negatives  from  paper  prints,  and  have  given 
some  useful  hints  by  which  the  disadvantages  to  which  they 
are  subject  can  be  reduced  to  a  minimum  (see  page  121). 

Paper  prints  naturally  remind  one  of  those  portrait 
albums  which  are  found  in  every  house.  Why  should  not 
these  pictures  also  be  adapted  to  the  lantern?    What  a 


208 


THE  BOOK  OF  THE  LANTEKtf. 


fund  of  interest  and  amusement  could  be  obtained  from 
an  exhibition  of  life-sized  pictures  of  friends  and  acquaint- 
ances well  known  to  the  family  circle  !  There  is  really 
no  great  difficulty  in  obtaining  such  pictures  when  the  first 
principles  are  understood;  and  when  practice  has  given 
experience,  negatives  from  prints  can  be  produced  with  a 
rapidity  and  certainty  to  which  the  most  experienced  land- 
scape photographer  is  a  stranger. 

Nor  must  the  young  folks  be  forgotten.  Although  the 
"  man  swallowing  rats  "  and  the  other  monstrosities,  known 
in  the  trade  as  "  comic  slips,"  still  have  an  attraction  to  the 
eye  of  youth,  surely  we  can  manage  by  the  means  now 
easily  within  reach,  to  place  before  the  youngsters  some- 
thing better  worth  looking  at.  The  quaintly  picturesque 
little  youths  and  damsels  drawn  by  Kate  Greenaway  would 
have  additional  charm  for  their  living  playfellows  if  shown 
life-sized  on  a  screen ;  and  nursery  legends,  as  interpreted 
by  Caldecott's  clever  pencil,  would  acquire  a  new  interest  if 
shown  in  the  same  fashion.  Perhaps  as  amateur  photo- 
graphy increases  its  number  of  workers,  as  it  is  rapidly 
doing,  artists  may  find  it  convenient  to  draw  subjects 
specially  for  reproduction  as  lantern  transparencies. 

There  is  one  feature  in  this  particular  class  of  photo- 
graphic work  which  I  have  not  yet  dwelt  upon,  and  that 
is,  the  possibility  of  producing  these  transparencies  inde- 
pendently of  daylight.  So  long  as  the  spring,  summer,  and 
autumn  days  are  upon  us,  the  possessor  of  a  camera  finds 
much  other  work  to  employ  his  time.  His  labours  are 
mostly  in  the  open  field,  adding  to  his  stock  of  negatives, 
and  he  looks  forward  with  regret  to  the  many  dark  hours 


THE  BOOK  OF  THE  LANTERN. 


209 


which  winter  must  bring,  in  which  such  work  is  impossible. 
But  now  is  his  time  for  lantern  preparation.  The  negatives 
are  looked  up  and  sorted  out,  and  by  means  of  a  gas  flame 
or  paraffin  lamp  he  can  print  off  transparencies  more 
quickly  than  even  on  a  favourable  day  he  could  produce 
paper  prints.  There  is  no  tedious  toning  or  extended 
washing  necessary,  and  therefore  the  work  does  not  entail 
half  the  trouble  that  he  is  accustomed  to  in  ordinary  print- 
ing. In  addition  to  these  advantages  there  is  one  other. 
A  transparency  on  glass  is  far  finer  in  effect  than  any 
paper  print,  for  the  reason  that  the  picture  is  absolutely 
without  texture.  Magnify  a  paper  print  and  the  texture 
of  the  paper  becomes  at  once  evident;  treat  a  good 
glass  positive  in  the  same  way  and  its  beauty  is  only 
increased. 

Lastly,  the  possessor  of  a  lantern  has  another  field  of 
work  in  which  it  can  be  usefully  and  efficiently  employed, 
— namely,  in  making  enlargements.  Not  the  evanescent 
and  fleeting  images  already  described,  but  permanent  en- 
largements of  a  quarter-plate  negative,  which  is  sufficiently 
rich  in  detail  and  interest  to  warrant  its  production  in  an 
enlarged  form.  By  means  of  an  oil  lantern,  and  a  sheet 
of  the  excellent  gelatino-bromide  paper  now  to  be  pur- 
chased, an  enlarged  positive  from  a  small  negative  is  easy 
to  produce.  And  here,  again,  the  work  is  quite  indepen- 
dent of  the  fickle  sun,  and  can  be  accomplished  in  any 
room  not  specially  set  apart  for  the  purpose. 

I  have  by  no  means  exhausted  the  list  of  services 
which  a  simple  form  of  optical  lantern  is  able  to  render, 
but  I  have  enumerated  several  which  will  serve  my  pur- 

P 


210 


THE  BOOK  OF  THE  LANTERN. 


pose  in  pointing  out  its  extreme  utility.  In  a  subsequent 
chapter  on  enlarging  I  dwell  in  detail  upon  the  various 
operations  necessary,  and  illustrate  them  by  diagrams, 
so  that  readers  may  acquire  a  practical  knowledge  of  the 
necessary  manipulations. 


CHAPTER  XV. 


THE  ART  OF  MAKING  PHOTO-MICROGRAPHS. 

PHOTO-MICROGRAPH  is  the  picture  of  a 
microscopic  preparation,  as  seen  by  the  eye 
when  enlarged  by  means  of  the  microscope; 
its  converse,  being  a  much-reduced  image  of  an  object 
photographed  on  glass,  which  is  called  a  micro-photograph, 
and  which  can  only  be  seen  when  placed  in  the  microscope. 
This  latter,  however,  is  a  mere  curiosity,  and,  although 
it  excites  some  wonder  when  looked  at,  has  no  educational 
or  scientific  value,  except  perhaps  as  a  proof  of  the  fine 
structure  of  a  photographic  film.  A  photo-micrograph,  on 
the  other  hand,  affords  a  valuable  means  of  displaying  to  a 
large  audience  the  delicate  structure  of  various  organisms, 
both  animal  and  vegetable  ;  besides  which  that  of  coal  and 
other  minerals  can  be  well  exhibited.  Lantern  micro- 
scopes,— some  of  very  beautiful  construction,— have  been 
brought  forward  from  time  to  time,  and  one  of  them,  at 
least,  I  shall  refer  to  in  a  subsequent  chapter. 

But  although  lantern  microscopes  may  give  very  fine 
results,  it  is  an  indisputable  fact  that  the  amount  of  light 
which  is  able  to  get  through  the  tiny  aperture  of  a  high- 
power  objective,  is  small.    And  when  this  small  amount 

v  2 


212 


THE  BOOK  OP  THE  LANTERN. 


has  to  be  spread  over  a  screen  of  even  moderate  propor- 
tions, the  illumination  of  the  whole  is  so  insufficient  that 
although  near  observers  are  able  to  note  that  the  disc  is 
covered  with  a  network  of  exquisite  detail,  those  who  are 
placed  a  few  yards  away  cannot  distinguish  anything  of  the 
kind.  If  this  is  the  case  with  those  whose  sight  is  perfect, 
how  much  more  true  it  must  be  of  the  large  number  of 
persons  who  are  less  favourably  endowed.  Probably  the 
difficulty  may  be  remedied  at  an  early  date  by  the  use  of 
the  electric  light,  which  is  far  more  brilliant  than  the  best 
limelight  possible,  and  I  know  that  experiments  are 
being  carried  on  in  this  direction !  In  the  meantime,  we 
must  look  for  other  means  of  projecting  the  image  of 
microscopic  objects  on  a  screen  if  we  require  such  illus- 
trations for  a  large  number  of  spectators.  I  recommend 
the  employment  of  photo-micrographs  of  the  size  of  the 
ordinary  lantern-slide,  viz.,  3^  x  3^  in.  as  the  best  way  out 
of  the  difficulty.  I  am,  of  course,  aware  that  a  photo- 
graph of  an  object  is  not  in  many  cases  so  good  as  the 
object  itself.  While  this  is  true,  it  is  also  true  that  there 
are  a  great  many  preparations  which  cannot  be  satisfactorily 
shown  by  any  kind  of  projecting  apparatus,  but  they  can 
be  made  to  yield  photographs  which  can  be  exhibited  by 
the  optical  lantern.  There  are  many  different  ways 
of  producing  photo-micrographs.  Some  workers  use  the 
most  complicated  apparatus,  whilst  others  seem  to  obtain  as 
good  results  with  rough  home-made  appliances.  But  so  it 
is  in  every  branch  of  science.  Somebody  wittily  divided 
microscopic  workers  into  two  different  species.  He  dubbed 
the  first  of  these  "  Brass  and  Glass,"  and  the  second 
"Bug  and  Slug."     The  first  are  the  possessors  of  the 


THE  BOOK  OF  THE  LANTERN, 


213 


magnificent  microscopes  with  all  kinds  of  movements  and 
expensive  attachments,  and  who  toy  with  their  instruments 
rather  than  work  with  them.  The  second  class  are  the 
hard  workers,  who  will  be  content  so  long  as  they  posse  ss 
one  or  two  good  powers,  and  have  anything  in  the  shape 
of  a  stand  to  hold  them  in  position.  They  will  accomplish 
far  more  real  work  with  a  simple  magnify ing-glass  than  one 
of  the  "  Brass  and  Glass  "  fraternity  with  his  gorgeous 
array  of  instruments. 

One  of  the  most  simple  methods  of  obtaining  a  photo- 
graph from  a  microscopic  object  is  to  use  a  little  camera, — a 
cardboard  box  with  a  hole  at  the  bottom  to  fit  over  the 
microscope  tube  is  sufficient, — placed  above  the  microscope 
as  it  stands  upright  on  a  table.  To  simplify  matters,  the 
eyepiece  of  the  microscope  should  be  removed, — a  method  of 
procedure  which  I  recommend  in  all  cases.  The  upper  part 
of  the  cardboard  box  should  be  furnished  with  a  lid  on  a 
hinge,  and  should  have  a  curtain  of  black  velvet  all  round  it, 
to  prevent  any  access  of  light.  On  its  inner  sides,  half  an  inch 
below  the  lid  opening,  should  be  glued  four  little  pieces  of 
wood  to  support  the  focussing  screen ;  the  same  support 
serving  later  on  to  hold  the  sensitive  gelatine -plate  in  posi- 
tion. Now  let  us  go  through  the  required  operations.  The 
image  is  focussed  by  daylight,  or  lamplight,  as  the  case 
may  be.  The  focussing  glass  is  then  removed,  and  while 
the  room  is  darkened  the  sensitive  plate  is  inserted  in  its 
place,  the  lid  of  the  box  shut  down,  and  all  is  ready  for  ex- 
posure. The  time  of  exposure  is  of  course  a  matter  depend- 
ing upon  a  host  of  circumstances  to  which  we  need  not  here 
refer.  The  exposure  having  been  made,  the  plate  is  de- 
veloped in  the  usual  manner. 


2H 


THE  BOOK  OF  THE  LANTERN. 


Another  plan  is  to  bring  down  the  microscope  to  the 
horizontal  position, —  and  most  microscopes  allow  of  this 
being  done, — and  to  pnsh  the  end  of  its  tube  into  the  flange 
opening  of  an  ordinary  photographic  camera,  with  the  lens 
of  the  latter  removed.  Bnt  both  these  methods  have 
a  disadvantage,  among  many  other  drawbacks,  which 
will  at  once  disappoint  the  operator.  The  image  afforded  is 
so  small.  The  tube  of  the  microscope  gets  in  the  way,  so 
to  speak,  and  a  large  portion  of  that  image  is  cnt  off.  This 
can  be  remedied  by  an  arrangement  of  the  apparatus  which 
I  am  now  about  to  describe,  and  by  which  I  have  taken  a 
number  of  photographs  which  leave  little  to  be  desired  in 
point  of  excellence,  while  the  necessary  manipulations  are 
carried  forward  with  that  ease  and  nicety  which  go  far  to- 
wards the  production  of  first-class  results. 

Let  it  be  at  once  pointed  out,  in  spite  of  the  opinions  of 
our  "  Brass  and  Glass  "  friends,  that  an  expensive  instru- 
ment is  not  required  for  this  work.  (Indeed,  I  will  presently 
point  out  how  it  is  possible  to  obtain  capital  photo-micro- 
graphs without  any  microscope  at  all,  although  the  essen- 
tial part  of  that  instrument, — the  objective, — must  be 
employed.)  What  is  wanted  is  a  good  firm  stand,  and  a 
fine  adjustment,  and  even  this  is  not  very  necessary  unless 
high  powers  are  employed.  But  the  majority  of  readers 
will  look  for  some  ready  means  of  photographing  objects  of  a 
popular  character.  The  proboscis  of  a  blowfly,  the  industrious 
flea  (or  bee  is  it  ?),  section  of  the  echinus  spine,  and  so  on ; 
such  things  as  can  be  readily  photographed  with  the  "  inch" 
objective.  And  to  readers  who  are  content  with  such  as 
these  I  chiefly  direct  my  remarks,  leaving  them  to  study 
the  excellent  treatises  and  articles  upon  the  subject  of 


THE  BOOK  OF  THE  LANTERN. 


215 


photo-micrography,  which  have  been  published,  when  they 
feel  themselves  capable  of 
higher  nights  in  this  most 
interesting    domain  of 
scientific  research. 

The  microscope  which 
I  use  is  of  a  very  ordinary 
pattern,  as  may  be  noticed 
in  the  diagram  (fig.  53) ; 
but  three  little  alterations 
in  it  make  it  very  con- 
venient for  photographic 
work.  In  the  front  leg 
of  the  claw-shaped  stand 
a  3-16ths  inch  hole  has 
been  bored,  so  that  the 
instrument  can  by  means 
of  a  screw  be  rigidly 
fixed  upon  a  base  board. 
The  next  alteration  is  in 
the  length  of  the  tube. 
Originally  seven  inches 
long,  I  have  had  it 
separated  at  nearly  the 
centre,  so  that  it  can  be 
reduced  to  three  inches  ; 
but  an  inner  tube  over 
which  the  outer  one 
tightly  fits,  allows  me  to 
use  the  microscope  for  ordinary  purposes  with  a  tube  of 


216 


THE  BOOK  OF  THE  LANTERN. 


normal  length.  The  third  modification  which  I  have  intro- 
duced, is  a  groove  cut  in  the  milled  head  of  the  fine  adjust- 
ment screw,  the  purpose  of  which  we  shall  presently  see. 
For  photographic  work,  the  mirror  is  thrown  out  of  gear, 
as  indicated  in  the  diagram,  for  it  is  not  required. 

Referring  once  more  to  this  diagram,  tt  is  the  table  on 
which  the  whole  arrangement  rests,  and  it  is  best  to  have 
a  table  for  the  purpose,  or  at  any  rate  a  level  base  board, 
upon  which  all  necessary  fixtures  can  be  made ;  c  is  a 
camera  which  should  open  out  to  great  extent  (most 
modern  cameras  are  made  to  do  so,  so  as  to  give  the 
photographer  the  benefit  of  using  long-focus  lenses) ; 
m  is  the  microscope,  s  the  stage,  p  the  mirror  thrown 
back  out  of  use,  n  the  coarse  adjustment,  and  k  the  fine 
adjustment.  We  can  now  see  the  advantage  of  providing 
this  milled  head  of  the  fine  adjustment  screw  with  a 
groove.  In  this  groove  is  p]aced  a  silk  cord,  which 
works  in  a  corresponding  groove  in  the  little  wheel 
which  is  fixed  on  the  end  of  the  focussing  rod  o  o.  By 
means  of  the  knob  d  at  the  other  end  of  this  rod,  the 
operator  is  able  to  work  the  fine  adjustment  to  a  nicety, — 
while  he  is  far  away  from  the  microscope, —  examining 
the  image  on  the  ground-glass  screen  of  the  camera. 

A  word  about  this  screen  will  not  be  amiss.  Ordinary 
ground-glass  will  not  do  for  this  class  of  work,  for  it  is 
far  too  coarse.  It  should  therefore  be  replaced  by  a 
focussing  screen  prepared  as  follows  : — Obtain  a  sensitive 
gelatine  plate,  such  as  is  used  for  negative  work,  expose 
it  to  the  light  of  a  gas  flame  for  a  second,  and  then  pro- 
ceed to  develop   it.     Develop  until   it  is  uniformly 


THE  BOOK  OP  THE  LANTERN. 


217 


darkened  to  a  small  extent,  fix  and  wash- in  the  usual 
manner,  and  then  bleach  it  in  a  solution  of  mercuric 
chloride.  The  result  will  be  a  plate  covered  with  an 
exquisitely  fine  translucent  surface,  upon  which  the 
finest  details  will  be  visible.  The  exact  amount  of 
exposure  and  development  to  secure  this  end  may  not 
be  at  first  hit  upon,  but  one  or  two  trials  will  be  sure  to 
end  in  a  satisfactory  result.  Some  workers  prefer  to  use 
a  plain  glass  upon  which  fine  lines  have  been  ruled 
with  a  writing  diamond.  In  any  case  the  worker  will 
find  the  advantage  of  supplementing  his  eyesight,  how- 
ever good,  by  a  focussing  glass.  In  this  way  a  far  sharper 
focus  is  obtainable  than  by  the  unaided  eye. 

To  describe  the  rest  of  the  diagram,  let  me  point  out 
that  /  is  an  ordinary  microscopic  paraffin  lamp,  furnished 
with  a  reflector  f,  and  that  h  is  a  condensing  lens,  having 
attached  to  it  a  diaphragm-plate,  e. 

Mr.  T.  Charters  White,  M.R.C.S.,  has  published  a 
method  by  which  photo-micrographs  can  be  produced 
without  the  aid  of  either  a  camera  or  a  microscope,  which 
is  very  creditable  to  his  ingenuity.  I  had  recently  the 
pleasure  of  hearing  him  describe  the  instrument,  while 
he  practically  demonstrated  how  effectually  it  would 
work.  The  apparatus  was  home  -  made,  and  such  as 
could  be  produced  by  any  one  with  the  minimum  of  out- 
side help,  although  there  are  many  accustomed  to  the  use 
of  tools  who  could  easily  make  it  without  any  help  at  all. 
I  appcmd  a  diagram  which  shows  the  various  parts  of  this 
simple  contrivance  (see  fig.  54). 

It  consists  in  a  lidless  box  sufficiently  large  to  con- 


218 


THE  BOOK  OF  THE  LANTERN. 


tain  an  ordinary  microscopic  lamp,  an  objective  which 
screws  into  one  end  of  the  box, — and  a  movable  stage 


Fig.  54. 


to  hold  the  object,  having  a  screw  attachment,  so  that 
it  can  be  moved  to  and  from  the  objective  in  order 
that  the  image  may  be  sharply  focussed  upon  a  plate 
held  in  a  frame  outside.  This  frame  is  fixed  to  a 
grooved  board,  which  can  be  moved  in  and  out  of  the  base 
board,  and  this  movement  determines  the  distance  of  the 
image  projected  from  the  Jens,  and  therefore  the  size  of 
that  image.  The  apparatus  may  indeed  be  compared  to 
an  optical  lantern  in  its  arrangements,  except  that  the 
condensing  lens  (an  ordinary  one  on  a  stand  such  as  is 
used  for  microscopic  work)  is  contained  within  the  box, 
and  that  the  object  to  be  projected  is  on  a  special  form  of 
movable  stage,  as  above  mentioned.  This  stage,  or  fine 
adjustment,  consists  of  two  parallel  and  horizontal  bars, 
with  a  fine  screw  of  the  same  length  laid  between  them, 
and  which  works  in  a  threaded  orifice  in  the  lower  part  of 
the  stage.    The  end  of  this  screw  nearest  the  light  is 


THE  BOOK  OF  THE  LANTERN. 


219 


crowned  with  a  grooved  wheel,  which  is  geared  by  a  piece 
of  cord  to  another  similar  wheel  at  the  end  of  a  focussing- 
rod,  which  is  brought  within  easy  reach  of  the  plate- 
carrier  outside  the  box. 

These  various  arrangements  will  be  rendered  clearer  by 
reference  to  the  diagram,  where  0  is  the  objective,  S  the 
stage,  F  the  focussing-rod,  L  the  lamp,  C  the  condenser, 
and  A  the  frame  holding  the  gelatine  plate,  or  the 
focussing-glass,  as  the  case  may  be,  for  one  takes  the 
place  of  the  other.  And  let  me  say,  in  passing,  that  this 
method  of  withdrawing  one  glass  so  that  the  other  can 
take  its  exact  place,  is  the  best  that  could  be  adopted,  for 
the  merest  fraction  of  difference  in  register  would  be 
perceptible  in  photo-micrographic  work,  while  it  might 
rimain  undiscovered  in  negative  taking  of  the  ordinary 
kind. 

Mr.  White's  apparatus  was,  at  the  time  I  saw  it,  fitted 
with  a  1-inch  objective;  but  he  told  me  that  he  had 
used  higher  powers  with  it.  It  certainly  is  capable  of 
very  fine  work,  as  was  proved  by  an  album  full  of  speci- 
mens which  he  exhibited.  His  focussing-screen  was  a 
plain  glass,  ruled  with  lines  by  a  -  diamond,  and  he 
employed  a  focussing  eye-piece.  But  it  is  evident  that, 
with  this  method  of  working,  the  operator  could  employ 
an  opaque  screen,  such  as  a  piece  of  opal  glass,  for  the 
room  in  which  the  work  is  carried  on  takes  the  place  of 
the  camera,  and  he  is  practically  within  it,  and  can 
look  upon  the  side  of  the  screen  which  is  next  the 
light.  By  means  of  a  scale  upon  the  sliding-board  which 
carries  the  gelatine  plate,  it  is  easy  to  note,  without  actual 


220 


THE  BOOK  OF  THE  LANTERN. 


measurement,  the  amount  of  magnification  of  the  image. 
And  this  magnification  can  be  carried  to  any  reasonable 
extent,  for  the  worker  is  not  limited,  as  he  would  be  if 
using  a  camera,  by  the  length  to  which  that  camera  can 
be  extended. 

But  perhaps  the  simplest  arrangement  of  all  is  that 
recently  introduced  by  Messrs.  Mawson  &  Swan,  and 
which  is  shown  at  fig.  55.    A  is  a  light  metal  disc,  which 


Fig.  55. 


can  be  screwed  on  the  camera  front  in  place  of  the  ordinary 
lens.  The  opening  in  its  centre  is  furnished  with  the 
regulation  microscopic  screw,  so  that  any  ordinary  micro- 
scopic objective  can  be  readily  fixed  to  it.  Upon  two 
horizontal  bars,  projecting  from  this  metal  disc,  there 
slides  another  similar  disc  B,  also  with  an  opening  in  the 
centre.  This  second  disc  has  fitted  to  it  a  pair  of  small 
spring  clips  for  the  reception  of  the  microscopic  slide 
which  it  is  desired  to  photograph.  Focussing  is  effected 
by  sliding  the  disc  B  to  and  fro  in  front  of  the  objective 


THE  BOOK  OF  THE  LANTERN. 


221 


on  A.  It  will  be  readily  seen  that  the  apparatus  may  be 
rendered  more  effective  by  the  attachment  of  a  screw,  or 
fine  adjustment  for  more  accurate  focussing  ;  but  with  the 
lower  powers  this  would  not  be  needed.  It  is  an  addition, 
however,  which  the  makers  will  supply  when  required. 

All  the  objectives  made  by  Messrs.  Swift,  as  well 
as  those  by  a  few  other  makers,  are  corrected  for 
photography,  but  in  those  of  older  date  the  visual  focus 
does  not  agree  with  the  chemical  focus.  As  a  rule,  no 
difficulty  will  be  found  with  the  higher  powers,  and  with 
the  others  a  few  trials  will  soon  show  what  allowance  in 
focussing  must  be  made.  As  a  rough  guide  to  what  must 
be  done  to  correct  this  fault,  which  is  rendered  evident 
by  a  sharply -focussed  image  appearing  blurred  in  the 
negative,  proceed  as  follows :  First  focus  the  image  as 
sharply  as  possible,  and  then  cause  the  objective  to 
approach  the  object  until  the  latter  seems  to  be  sur- 
rounded by  a  reddish  light;  now  take  the  photograph 
and  it  will  be  sharply  defined,  although  the  image  did  not 
look  so  on  the  focussing  screen. 

The  ferrous-oxalate  method  of  development,  described  on 
a  former  page,  is  very  suitable  for  negatives  taken  for 
photo-micrographs.  These  negatives  are  then  made  to 
furnish  lantern  slides  in  the  manner  detailed  in  a  former 
chapter. 


CHAPTER  XVI. 


mm 


ENLARGING  PHOTOGRAPHS  WITH  THE  LANTERN. 

HE  amateur  who  works  with  a  quarter  plate 
camera  will  often  congratulate  himself  upon 
the  slight  burden  which  it  entails,  even  when 
several  double  backs  and  spare  plates  accompany 
it.  But  he  will  also  regret  that  the  little  pictures 
which  it  yields, — measuring  only  3  by  4  inches  when 
trimmed  and  finished, — are,  after  all  his  trouble,  so 
very  insignificant-looking.  He  may  possibly  have  availed 
himself  of  the  instructions  already  given  for  the  produc- 
tion of  lantern  slides  from  such  small  negatives,  and  thus 
ascertained  that  his  pictures  are  full  of  detail,  and  will 
bear  enlargement.  But  lantern  images  are  fleeting  things, 
— dissolving  views,  in  truth, — and  he  would  fain  endeavour 
to  find  some  more  permanent  way  of  increasing  the  size 
of  his  pictures.  Thanks  to  the  wronderful  photographic 
revolution  achieved  by  gelatine  emulsion,  this  can  be  done 
without  very  much  trouble  or  difficulty. 

In  using  the  lantern  for  exhibition  purposes  we  employ 


THE  BOOK  OF  THE  LANTERN. 


223 


for  slides  transparent  positives  on  glass,  and  it  stands  to 
reason  that,  if  the  sheet  or  surface  upon  which  the  image 
is  thrown  were,  by  chemical  means,  to  be  made  sensitive 
to  light,  we  should  obtain  much  the  same  result  that  we 
get  by  means  of  our  camera, — a  negative  image,  which  can 
be  rendered  visible  by  development.  If,  on  the  other  hand, 
we  employ  one  of  our  little  negatives  as  a  lantern  slide, 
we  can  produce  from  it  a  positive.  Such  is  the  theory 
which  we  will  now  endeavour  to  reduce  to  practice. 

The  lantern  employed  can  be  of  the  ordinary  kind  used 
for  projection,  but  in  this  case,  where  the  condenser  only 
measures  4  inches,  it  is  obvious  that  a  negative  measuring 
less  than  that  size  will  be  the  only  one  available.  The 
operator  will  therefore  be  better  off  with  a  lantern  made 
specially  for  enlarging  purposes,  the  condenser  of  which 
must  be  at  least  5  inches  in  diameter  to  accommodate  a 
quarter-plate  negative.  It  might,  in  many  cases,  be  prac- 
ticable to  fit  the  ordinary  lantern  with  a  condenser  of  that 
size  when  it  is  proposed  to  use  it  for  enlarging  purposes. 
Whatever  be  the  arrangement,  there  must  be  in  front  of 
the  lens  of  the  lantern  a  flat  board  upon  which  the  image 
can  be  projected,  and  which  will  serve  as  a  support  for  the 
sensitive  surface  at  a  later  stage  of  the  operations. 

A  convenient  form  of  upright  easel  is  shown  at  fig.  56.  It 
can  be  moved  backwards  and  forwards  between  a  couple  of 
laths  nailed  on  the  floor,  while  the  enlarging  lantern 
remains  stationary.  A  light-tight  box  above  it  contains  a 
roll  of  sensitive  paper,  which  can  be  pulled  down  and  cut 
off  in  lengths  as  required.  This  easel  has  a  hinged  frame, 
so  that  when  a  sufficient  length  of  the  paper  is  drawn  down 


224 


THE  BOOK  OF  THE  LANTERN. 


over  the  face  of  the  easel,  which  serves  as  a  focussing 
board,  the  frame  shuts  it  in  and  is  clamped.    In  this  way 


Fig.  56. 

the  paper  is  held  tight  without  the  necessity  of  using  pins, 
or  other  loose  fastenings. 

Fig.  57  shows  a  larger  view  of  this  box,  with  its  supply 
of  sensitive  material.  But  the  beginner  would  no  doubt, 
first  of  all,  experiment  with  a  simple  board,  and  one 
measuring  12  inches  by  10  inches  would  be  ample. 

The  sensitive  surface  to  be  employed  when  a  direct 
positive  is  required,  is  paper  specially  prepared  with  a 


THE  BOOK  OF  THE  LANTERN. 


225 


coating  of  gelatino-bromide  of  silver  emulsion.  If  an 
enlarged  negative  is  desired,  either  an  ordinary  gelatine 
(glass)  plate  of  the  required  size  may  be  employed,  or  a 
paper  negative  can  be  made  in  the  manner  to  be  presently 
described.    Messrs.  Morgan  &  Kidd,  of  Richmond,  were 


Fig.  57. 


the  first  to  introduce  "  argentic  gelatino-bromide  paper," 
and  therefore  the  circumstance  should  be  noted  to  their 
credit.  It  can  now  be  obtained  from  most  other  dealers, 
and  its  manufacture  is  so  well  understood  that  it  will  be 
found  generally  reliable.  It  can,  of  course,  be  used  for 
contact  printing  as  well  as  for  enlarging  purposes.  But 
perhaps  the  sanguine  amateur  may  prefer  to  manufacture 
it  for  himself,  and  there  is  no  reason  why  he  should  not 
succeed  in  doing  so,  if  he  is  already  master  of  the  secret  of 
making  an  emulsion  which  neither  fogs  nor  frills.  Here 
is  a  necessarily  brief  outline  of  the  method  of  going 
to  work  : — 

Procure  some  good  plain  Saxe  paper.  Having  made 
and  fiHered  your  emulsion,  allow  it  to  set  to  a  jelly  in  a 

Q 


226 


THE  BOOK  OF  THE  LANTERN. 


dish.  With  a  good  stiff  hog-hair  stencil-brush  break  up 
the  cold  jelly,  and  rub  it  vigorously  over  the  paper,  just  as 
you  would  break  up  cold  starch  jelly  in  mounting  prints. 
Now  drag  the  paper  slowly  over  an  earthenware  foot- 
warmer,  which  has  been  duly  charged  with  boiling  water. 
The  heat  will  cause  the  little  specks  of  jelly  on  the  paper 
to  melt  and  mingle,  and  the  whole  will  present  a  smooth 
surface.  The  paper  must  now  be  hung  up  to  dry,  or  it 
may  be  used  at  once.  I  need  hardly  say  that  all  these 
operations  must  be  conducted  by  non-actinic  light.  The 
majority  of  workers,  however,  will  prefer  to  buy  their 
argentic  paper  ready-made,  and,  by  doing  so,  save  them- 
selves possibly  much  vexatious  disappointment. 

Any  room  will  serve  for  the  purpose  of  making  an 
enlargement ;  but  it  is  preferable  to  conduct  the  work 
at  night,  because  then  is  saved  the  trouble  of  darkening 
a  room  so  that  it  is  really  fit  for  photographic  opera- 
tions, by  no  means  an  easy  matter.  Having  a  dark 
room,  the  further  requirements  are  a  lantern,  a  screen 
as  aforesaid  in  front  of  it,  with  a  sheet  of  white  paper 
pasted  over  its  surface,  a  good  red  lamp,  a  developing 
dish,  the  necessary  chemicals,  and,  lastly,  plenty  of  water 
and  a  pail  for  waste  solutions.  If  the  room  has  in 
it  a  tap  and  sink,  so  much  the  better.  The  negative 
(which  should  be  a  good  one,  or  it  will  not  be  worth 
enlarging)  is  placed  in  the  lantern  like  an  ordinary  slide, 
taking  care  that  the  film  side  is  turned  towards  the  screen, 
and  away  from  the  light.  Now  carefully  focus  its  image 
on  the  white  board.  Having  placed  lantern  and  screen  at 
such  a  distance  from  one  another  that  the  image  is  of  the 


THE  BOOK  OF  THE  LANTERN. 


227 


required  dimensions,  and  having  seen  that  that  image  is 
as  sharply  focnssed  as  possible,  it  will  be  as  well  if  a  slip 
of  sensitive  paper,  say,  1  inch  wide,  is  first  of  all  exposed 
as  a  pilot. 

In  the  hnrry  and  bustle  incidental  to,  if  not  inseparable 
from,  every-day  life,  we  all  have  a  tendency  to  work  too 
much  by  rnle  of  thumb,  and  it  must  be  confessed  that  rule 
of  thumb  often  turns  out  very  good  results.  But,  in  spite 
of  this,  and  of  the  old  adage  to  the  effect  that  an  ounce  of 
practice  is  worth  a  pound  of  theory,  we  cannot  afford  to 
give  theory  the  go-by  entirely.  Theory  is  a  useful  servant, 
but  a  bad  master,  for  those  patient,  plodding  creatures  who 
think  of  nothing  else  seldom  turn  out  work  which  has  the 
stamp  of  genius  upon  it.  Theory  holds  them  down  in  her 
rigid  grasp,  and  they  have  not  the  pluck  to  try  anything 
or  dare  anything  that  seems  opposed  to  her  teachings.  If, 
on  the  other  hand,  theory  be  regarded  as  a  reliable  servant, 
to  be  consulted  when  difficulties  occur  in  practice,  her 
value  will  soon  be  recognised. 

These  thoughts  came  into  my  mind  once  when  watching 
a  young  experimenter,  who  was  endeavouring  to  make 
some  enlargements  on  bromide  paper  from  small  negatives, 
by  means  of  an  oil  lantern.  The  negative  was  placed 
on  the  stage  of  the  lantern,  and  its  image  was  projected 
upon  the  side  of  a  wooden  packing-case,  which  stood  on 
the  table  in  front  of  it.  My  young  friend  was  endeavour- 
ing to  make  from  his  small  negative  (|-plate)  enlarged 
copies  of  different  sizes ;  and,  to  obtain  the  different  sized 
images,  he  had,  of  course,  to  move  the  focussing  surface 
either  to  or  from  the  lens  as  the  image  was  required  to 

Q  2 


228 


THE  BOOK  OF  THE  LANTERN. 


be  smaller  or  larger.  But  with  regard  to  exposure  he 
worked  entirely  by  rule  of  thumb,  or  rather,  I  might 
say,  by  no  rule  at  all.  It  was  all  guesswork,  and, 
although  he  tried  many  pilot  slips  of  paper  with  watch  in 
hand,  he  failed  to  turn  out  any  really  correctly-exposed 
pictures.  His  failure  was  chiefly  due  to  his  utter  ignorance 
of  the  law  in  optics,  which  has  been  already  considered 
on  page  118. 

Referring  once  more  to  fig.  39  on  that  page,  let  the  four 
squares  numbered  1,  2,  3,  and  4,  be  printing-frames 
placed  at  distances  of  1,  2,  3,  and  4  feet  from  a 
candle-flame.  Let  us  suppose,  also,  that  we  have  ascer- 
tained by  experiment  that  the  plate  or  paper  in  the  first 
position  (No.  1)  is  sufficiently  affected  by  the  light  if  it 
remain  there  for  one  minute.  (This  is,  of  course,  merely 
stated  as  a  case  in  point.  Bromide  paper  at  such  a  distance 
would  be  sufficiently  exposed,  under  a  normal  negative,  in 
about  eight  seconds,  while  a  chloride  plate  under  such  con- 
ditions would  want  two  minutes  or  more.)  Then,  if  we  re- 
move the  frame  to  position  No.  2 — at  2  feet  from  the  light 
source  — the  necessary  exposure  will  not  be  doubled,  as  some 
might  think,  but  quadrupled.  For  the  square  of  2  is  that 
number  multiplied  by  itself, — i.e.,  4.  The  right  exposure, 
therefore,  will  be  four  minutes.  Removing  the  frame  to 
position  3,  we  must  once  more  square  that  number  in 
order  to  arrive  at  the  right  number  of  minutes,  for  ex- 
posure at  this  increased  distance.  3  x  3  =  9.  Therefore 
nine  minutes  Avill  be  the  time.  It  is  easy  to  see  that  when 
the  printing-frame  is  removed  to  the  farthest  distance  of 
all,  which  is  4  feet  from  the  light  source,  the  exposure 


TI1E  LOOK  OF  THE  LANTERN. 


229 


will  be  sixteen  minutes.  To  make  the  diagram  more 
explicit,  the  vertical  squares  1,  2,  3,  and  4,  have  been  so 
subdivided  that  the  number  of  spaces  in  each  indicates 
the  number  of  units  of  exposure,  be  that  unit  a  second,  a 
minute,  or  an  hour.  The  same  rule  holds  good  for  en- 
larging operations.  Thus,  supposing  that  we  are  working 
with  an  optical  lantern,  and  that  the  necessary  exposure 
at  1  foot  from  the  lens  is  half  a  minute  ;  at  2  feet  the 
time  will  be  two  minutes ;  at  3  feet  four  minutes  and 
a  half  ;  and  so  on.  The  practical  worker  will  have  this 
little  bit  of  theory  in  his  mind  whenever  he  is  operating, 
and  he  will  soon  be  convinced  that  the  theory  is  strictly 
correct. 

Another  help  in  enlarging,  which  will  be  found  useful, 
is  a  little  piece  of  apparatus, — if  it  can  be  dignified 
by  that  name, — which  I  have  lately  made,  and  which  I 
call  an  exposing-gauge.  It  is  so  simple  in  construction 
that  any  one  can  make  it  out  of  a  couple  of  strips  of  card- 
board. The  arrangement  is  shown  in  fig.  57.  The  size 
of  the  gauge  is  immaterial,  but  a  length  of  20  inches 
will  be  found  convenient.  A  slip  of  card  of  that  length, 
and  about  1  inch  in  breadth,  is  cut  with  pointed  ends, 
each  point  having  a  hole  pricked  in  it  as  shown.  By  these 
holes,  and  with  the  assistance  of  a  couple  of  drawling-pins, 
the  contrivance  can  be  readily  attached  to  any  flat  surface 
upon  which  the  enlarged  image  from  the  lantern  is 
focussed.  Placed  above  this  slip  is  another  piece  of  card 
slightly  shorter,  and  with  a  round  hole  in  the  centre.  The 
two  strips  are  bound  together  with  pieces  of  tape  glued 
over  their  upper  and  lower  edges,  the  two  ends  being  left 


230 


THE  BOOK  OF  THE  LANTERN. 


open,  like  a  sleeve,  for  the  reception  of  a  slip  of  paper 
like  that  shown  in  fig.  58. 

Fig.  58. 

<$k~     ^   *  Q>  •  ^  1> 

>   I  «  M  l  c  1  g  1  *  ij  < 

Fig.  59. 

Fig.  59,  as  indicated,  really  consists  of  two  slips  of  paper 
gummed  together  end  to  end.  One  is  sensitive  bromide 
p  per,  ten  inches  in  length,  which  has  been  spaced  out 
into  five  divisions,  and  marked  a,  b,  c,  d,  e,  with  an  aniline 
ink  pencil.  The  other  part  is  ordinary  white  cartridge 
paper,  slightly  longer  than  the  sensitive  slip.  Its  purpose 
is  to  serve  as  a  handle  by  which  to  pull  the  sensitive  paper 
through  the  sleeve,  and  also  to  furnish  a  white  surface 
upon  which  a  small  part  of  the  picture  can  be  focussed, 
that  small  part  being  confined  to  the  central  circular  hoi 
in  the  upper  card. 

Now  let  us  see  how  the  gauge  is  used  in  practice.  It  is 
first  pinned  on  the  focussing  board  so  that  a  distinctive 
part  of  the  image  is  thrown  upon  the  central  hole.  In  the 
case  of  a  portrait  this  should  be  the  eye.  Having  focussed 
carefully  on  the  blank  paper,  the  first  division  of  the 
sensitive  slip,  which  will  be  that  marked  e,  is  pulled  in 
front  of  the  opening.  Let  this  be  exposed  for,  say,  fifteen 
seconds ;  then  pull  the  slip  onwards,  and  expose  d  for 
twenty  seconds,  c  for  twenty-five  seconds,  and  so  on.  The 
gauge  is  then  taken  into  the  dark  room,  its  slip  of  sensitive 
paper  taken  from  its  yoke-fellow,  and  carefully  developed. 


THE  BOOK  OF  THE  LANTERN. 


231 


It  will  then  soon  be  seen  which  of  the  lettered  spaces  has 
received  the  correct  exposure ;  and  a  memorandum  noting 
time  and  distance  of  lens  from  screen  can  either  be 
attached  to  the  negative,  or  entered  in  a  book  against  a 
number  corresponding  with  a  number  scratched  on  the 
glass  negative. 

The  same  principle  can  be  applied  to  contact  printing 
in  a  frame  on  bromide  paper,  by  gas  or  lamp  light.  When 
the  frame  has  been  charged  with  its  negative  and  the 
bromide  paper,  support  it  upright  at  a  distance  of,  say, 
18  inches  from  the  turned-down  flame.  Now,  place 
in  front  of  it  an  opaque  card,  sufficiently  large  to  more 
than  cover  the  frame.  This  card  should  have  a  hole  about 
1  inch  in  diameter  cut  in  it  in  one  corner.  Turn  up  the 
light  and  expose  for  five  seconds.  Alter  the  position  of  the 
hole  and  give  ten  seconds,  and  so  on.  When  the  paper  is 
subsequently  developed  the  several  exposures  can  be 
readily  identified,  and  the  negative  can  be  labelled  to  the 
effect  that  it  requires  so  much  exposure  at  a  given  distance 
from  a  flame.  Thus — Bromide  paper,  18  in.  25  sec.  This 
negative  will  then  be  an  infallible  guide  for  the  exposure 
of  negatives  of  a  similar  type ;  for  a  systematic  worker, 
unless  he  be  quite  a  beginner,  will  fall  into  the  way  of 
producing  negatives  of  much  the  same  character  and 
strength,  and  printing  from  them  by  lamp  light  will  then 
become  an  easy  matter  to  hijn. 

After  this  somewhat  long  but  not  unnecessary  digression, 
I  will  resume  my  directions  for  enlarging  on  bromide 
paper,  and  for  the  sake  of  simplicity  will  suppose  that  the 
operator  is  not  supplied  with  the  special  form  of  easel 


232 


THE  BOOK  OF  THE  LANTERN. 


which  I  have  referred  to,  but  is  using  a  mere  board  for  the 
purpose. 

The  paper  is  supplied  in  cases,  either  in  flat  sheets,  or 
rolled  with  the  sensitive  surface  inwards.  A  piece  of  the 
required  size  is  pinned  on  the  focussing  board  \  and  the 
best  way  to  do  this  is  to  pin  the  two  upper  corners 
first,  and  to  unfold  the  paper  over  the  board,  pinning  it 
down  at  the  edges  as  required.  Drawing-pins  will  do,  but 
ladies'  bonnet  pins  are  much  more  easily  handled  in  the 
semi-darkness  of  the  room.  Now  uncover  the  lens  for  the 
proper  time,  and  be  careful  that  the  lantern  is  quite  free 
from  vibration.  If  you  wish  the  picture  to  be  vignetted, 
this  is  most  easily  managed  during  exposure.  A  piece  of 
brown  paper,  a  foot  square,  is  cut  in  the  centre  with  an 
oval  opening,  with  a  serrated  edge.  Hold  this  in  front  of 
the  lens,  and  keep  it  in  gentle  movement,  so  that  the 
pointed  edges  of  the  paper  are  always  changing  their  places. 
This  will  cause  the  edges  of  the  picture  to  be  ill-defined, 
and  a  white  margin  will  be  left  outside  them. 

I  need  hardly  point  out  that  in  enlarging  by  this  method 
the  operator  has  a  wonderful  amount  of  controlling  power 
at  his  disposal,  in  bringing  out  certain  parts  of  the  picture 
with  extra  density,  and  reducing  those  parts  which  may 
require  such  treatment.  Thus  the  distant  portion  of  a 
landscape  may  be  lightened  by  a  card  moved  with  discre- 
tion over  that  part  of  the  image  during  exposure.  If,  too, 
some  point  in  the  negative  is  of  unusual  density,  it  can 
receive-  extra  exposure  by  using  a  card  with  a  hole  in  it, 
in  front  of  the  easel. 

At  the  end  of  the  exposure  the  lantern  is  capped,  the 


THE   BOOK  OF  THE  LANTERN. 


233 


paper  is  unpinned,  and  carried  to  the  developing  dish.  It 
is  now  saturated  with  cold  water  on  both  sides,  and  clean 
hands  may  assist  in  spreading  the  water  over  the  surface 
until  it  lies  perfectly  flat  on  the  bottom  of  the  tray.  The 
water  is  now  drained  off  and  the  developer  applied.  The 
ferrous  oxalate  method  is  by  far  the  best  to  adopt,  but  the 
proportion  of  iron  should  be  reduced  to  about  one-sixth,  or 
even  one-eighth  of  the  oxalate  solution ;  and  to  insure  the 
best  results,  the  exposure  should  be  such  that  only  a  very 
small  dose  of  bromide  solution  is  necessary.  Some  workers 
prefer  to  bring  the  image  out  slowly  by  using  an  old 
ferrous  oxalate  solution.  I  myself  prefer  it  mixed  per- 
fectly fresh,  and  am  quite  certain  that  if  the  best  results 
are  looked  for,  fresh  developer  should  be  mixed  for  every 
print  required.  The  development  must  not  be  carried  too 
far,  for  the  image  gains  in  density  under  fixation.  When 
development  is  judged  to  be  complete,  drain  off  the  liquid, 
and  immediately,  without  washing,  flood  the  surface  of  the 
picture  with  an  acid  solution. 

Acetic  acid  (glacial)    1  drachm. 

Water  ...        ...        ...        ...    16  ounces. 

The  addition  of  this  solution  keeps  the  whites  of  the  pic- 
ture pure.  In  a  minute  or  two  pour  the  acid  away,  wash 
the  print,  and  fix  in  fresh  hypo  of  the  usual  strength.  The 
print  ought  to  be  fixed  in  about  ten  minutes  ;  if  it  is  allowed 
to  remain  in  the  hypo  longer  than  necessary  the  half-tones 
are  quickly  destroyed.  Now  wash  the  paper  in  several 
changes  of  water,  and  let  it  soak  for  a  couple  of  hours  at 
least  before  drying. 

It  is  not  very  difficult  to  print  in  clouds,  from  a  separate 


234 


THE  BOOK  OF  THE  LANTERN. 


negative,  on  an  enlarged  positive  on  bromide  paper.  The 
process  depends  npon  the  circnmstance  that  the  paper 
remains  sensitive  to  light, — but  in  a  diminished  degree, — 
after  the  developing  solution  has  been  applied  to  it,  Pro- 
ceed as  follows  : — Expose  your  landscape  as  usual,  but  stop 
development  before  the  required  density  is  obtained,  and 
wash  the  paper.  Now  placing  your  cloud  negative  in  the 
lantern,  pin  up  the  paper  once  more,  shielding  the  land- 
scape portion  by  a  piece  of  card  kept  in  movement,  and 
give  another  exposure.  Now  re-develope  to  the  right 
density,  and  you  will  find  that  while  the  landscape  gains 
in  strength  the  clouds  will  become  faintly  apparent.  The 
picture  can  then  be  fixed  and  finished  according  to  the 
directions  given. 

If  several  copies  of  an  enlargement  are  required,  the 
best  method  will  be  to  make  an  enlarged  negative  on 
paper,  using  a  glass  positive  (an  ordinary  lantern  slide)  in 
the  lantern.  The  same  operations  as  those  just  described 
are  necessary,  but  the  exposure  can  with  advantage  be 
increased.  I  should  also  recommend  the  use  of  alkaline 
development,  and  I  think  that  washing  soda  and  pyro  is 
the  best  form  of  it  for  the  purpose.  The  paper  negative 
when  dry  is  rendered  transparent  by  being  passed  through 
a  bath  of  melted  paraffin  wax.  It  can  then  be  used  in 
an  ordinary  printing- frame  to  produce  prints  as  may  be 
desired. 

Some  time  ago  I  published  a  new  method  of  obtaining 
enlarged  negatives,  which  will  be  useful  to  those  who  wish 
to  work  with  an  ordinary  lantern,  and  who  are  ready  to 
undertake  the  task  of  plate-making, 


THE  BOOK  OF  THE  LANTERN. 


235 


I  had  occasion  to  obtain  from  some  half-plate  negatives 
some  copies  of  them  on  plates  measuring  16  by  13.  The 
problem  I  put  to  myself  was  this, — which  is  the  quickest 
and  best  way  of  accomplishing  the  work  ?  After  some 
consideration  I  determined  to  work  with  the  limelight, 
for  the  weather  was  dull  and  uncertain  at  the  time  I  am 
speaking  of,  and  1  thought  that  I  would  at  once  eliminate 
one  common  source  of  error  by  adopting  a  mode  of  illumi- 
nation which  represents  a  constant  quantity.  This  being 
settled,  I  next  thought  over  the  different  systems  of  en- 
larging, and  finally  decided  to  try  a  new  plan. 

I  am  so  constantly  using  the  lime-light  for  lecture 
purposes,  that  a  residue  of  oxygen  is  always  at  hand, 
ready  for  any  home  experiment  that  I  like  to  try  ;  other- 
wise, I  should,  perhaps,  have  decided  to  carry  out  my  plan 
with  some  other  illummant.  Fitting  a  blow-through  lime- 
jet  to  an  experimental  lantern  with  a  4-inch  condenser, 
and  with  a  quarter-plate  portrait  lens  as  the  objective,  my 
optical  arrangements  were  complete.  But  a  4-inch  con- 
denser is  clearly  useless  for  projecting  the  image  of  a 
negative  nearly  double  its  area.  My  first  operation  was, 
therefore,  to  make  some  small  positives  on  glass  from  the 
negatives.  This  was  easily  done  by  fitting  the  negatives 
into  my  copying  apparatus,  and  using  a  quarter-plate 
camera.  The  size  of  the  resulting  positives  was  just  two 
inches  across ;  smaller,  it  may  be  thought,  than  was  abso- 
lutely necessary.  But,  by  this  plan,  I  employed  the  best 
part  of  the  projecting  lens,  and  there  was  no  chance  of  any 
falling  off  in  sharpness  at  the  margin  of  the  pictures. 

The  small  positives  were  made  with  very  great  care,  the 


236 


THE  BOOK  OP  THE  LANTERN. 


exposure  and  development  being  so  controlled  that  the 
resulting  pictures  were  somewhat  denser  than  would  be 
advisable  for  an  ordinary  lantern-slide.  They  exhibited  in 
miniature  every  detail  to  be  found  in  the  negatives  to 
which  they  owed  their  origin  ;  and,  in  more  than  one  case, 
an  improvement  was  effected  in  the  process  of  reduction, 
for  some  of  the  negatives  were  yellowed  in  certain  portions, 
and  would,  therefore,  print  unequally.  This  was  obviated 
by  shading  during  exposure. 

The  positives,  although  measuring  only  2  inches  across, 
were  taken  for  convenience  on  the  standard  plates  for 
lantern  pictures,  3^  by  3^ ;  so  that  a  broad  margin  of 
clear  glass  remained  all  round  them.  This  was  covered 
with  black  varnish,  after  which  the  glasses  were  fitted  into 
the  usual  grooved  carriers  employed  in  lantern  work. 

The  next  thing  was  to  arrange  a  proper  focussing-screen 
for  the  reception  of  the  image.  This  took  the  form  of  a 
sheet  of  glass,  16  by  13,  covered  on  one  side  with  white 
paper.  Temporary  wooden  c  ips,  fastened  to  the  wall  at  a 
convenient  height  from  the  ground,  held  this  papered  glass 
in  position,  and  in  such  a  way  that  it  could  be  readily  re- 
moved and  a  sensitive  plate  put  in  its  place. 

It  is  with  regard  to  the  sensitive  plates  that  I  must  now 
speak.  I  found  that  commercial  plates  of  the  size  required, 
16  by  13,  were  very  expensive;  if  I  remember  rightly,  some- 
thing like  £2  per  dozen  was  the  price  quoted  to  me.  This 
was  more  than  I  cared  to  expend  on  mere  experimental 
work  j  besides  which,  it  goes  against  the  grain  to  buy 
plates  when  one  has  been  in  the  habit  for  years  of  making 
them  of  unsurpassed  quality.    I  now  bethought  me  that  I 


THE  BOOK  OP  THE  LANTKRN. 


23t 


had  put  away  somewhere  a  jar  of  chloride  emulsion,  which 
I  had  made  some  months  before,  and  had  left  neglected  for 
want  of  opportunity  to  make  plates  from  it.  Why,  thought 
I,  should  I  not  make  some  16  by  13  plates  with  this 
chloride  emulsion  ?  The  thing  was  no  sooner  conceived 
than  put  in  practice,  and  that  night  the  plates  were  coated 
and  racked,  to  the  number  of  eighteen.  I  also  was  careful 
at  the  same  time  to  cover  a  few  quarter-plates,  with  which 
I  could  make  trial  exposures. 

There  is  one  great  advantage  in  manipulating  chloride 
emulsion  and  the  plates  made  from  it :  it  is  so  insensitive 
— about  100  times  less  so  than  bromide  plates — that  the 
brightest  of  yellow  lights  can  be  used  without  affecting  it. 
I  use  a  brilliant  paraffin  lamp,  surrounded  by  a  wire  fence, 
and  tl*is  is  covered  with  a  screen  of  yellow  oiled  p:iper. 
The  light  given  is  so  great  that  a  book  can  easily  be  read 
at  the  further  end  of  the  room,  and  my  coating-room  is 
quite  a  large  one. 

Two  days  later  I  was  reidy  for  work,  and  had  the 
lantern  adjusted  at  the  right  distance  from  my  focussing- 
screen  on  the  wall  to  give  an  image  of  the  required  size. 
Carefully  focussing  the  first  picture,  I  took  one  of  the 
little  trial -plates,  and  held  it  against  the  focussing  screen 
for  one  minute.  Upon  development  it  showed  under- 
exposure. One  or  two  more  trials  resulted  in  my  finding 
that  the  correct  exposure  was  ninety -five  seconds.  I  now 
felt  some  confidence  in  dealing  with  the  larger  plates,  and 
I  exposed  three,  one  after  another. 

Now  came  the  development.  1  mixed,  first  of  all,  one 
pint  of  developer  from  my  stock  solutions,  and  this  I  put 


238 


THE  BOOK  OF  THE  LANTERN. 


into  a  jug.  The  first  plate  was  put  into  a  dish,  and  the 
whole  jugful  swished  over  it.  The  image  flashed  out  at  once. 
This  is  always  the  case  with  my  chloride  plates,  so  that  it 
did  not  surprise  me  Keeping  the  developer  moving  over 
the  plate,  I  lifted  up  the  glass  at  intervals  so  as  to  watch 
its  progress.  In  about  four  minutes  it  had  attained 
sufficient  density.  I  then  emptied  the  developer  back  into 
the  jug,  for  I  knew  it  would  serve  for  several  plates  in 
succession.  The  negative  in  the  dish  was  now  thoroughly 
washed  with  about  a  gallon  of  water,  and  transferred  to 
the  fixing-bath.  The  remaining  plates  were  then  treated 
in  exactly  the  same  way,  and  without  a  single  failure. 

There  was  at  first  some  difficulty  in  thoroughly  washing 
such  large  plates,  but  I  solved  it  by  making  use  of  the 
bath-room.  The  bath  was  filled  with  water,  and  the 
plates  were  placed  along  the  sides,  film-side  down.  In  less 
than  an  hour  they  were  thoroughly  freed  of  the  fixing  salt. 

These  negatives  were  all  that  could  be  desired.  Some 
of  them  were  purposely  reversed  for  printing  by  the 
carbon  process,  this  reversal  being  brought  about  by  the 
simple  expedient  of  causing  the  film-side  of  the  little 
positive  to  face  the  light  in  the  lantern.  Their  perfection 
of  detail  may  be  gauged  by  the  following :  In  one  case  the 
little  positive  had  become  rather  dusty  previously  to 
exposure,  and  I  took  it  out  of  the  lantern,  and  rubbed  its 
varnished  surface  with  my  handkerchief.  This  caused 
some  tiny  scratches  upon  it,  which  were  at  the  time  quite 
unnoticed ;  but  the  scratches  were  clearly  visible  on  the 
enlarged  negatives.  They  were,  certainly,  not  thicker 
than  the  finest  spider's  web, — but  still,  there  they  were. 


THE  BOOK  OF  THE  LANTERN. 


239 


I  have  already  indicated  how  this  work  of  enlarging 
can  be  done  with  an  ordinary  optical  lantern,  so  long  as 
the  size  of  the  negative  is  not  above  that  of  a  lantern 


slide.  For  larger  negatives  it  is  far  better  to  use  a  proper 
enlarging  lantern  of  the  type  shown  at  fig.  60. 


CHAPTER  XVII. 


THE  LANTERN  MICROSCOPE  AND  THE  OPAQUE  LANTERN. 


P  to  a  recent  date  the  so-called  lantern  micro- 
scope supplied  by  various  dealers  was  but  a  toy, 
having  all  the  faults  which  it  was  possible  to 
imagine  in  an  optical  instrument.  Moreover,  it  neces- 
sitated the  use  of  specially  prepared  objects  of  large  size, — 
the  wings  of  insects  and  the  like.  But  latterly  a  good  deal 
of  ingenuity  has  been  expended  on  the  instrument,  and  it 
has  been  brought  to  great  perfection.  Objects  as  prepared 
for  the  ordinary  microscope  can  now  be  used  for  projection 
in  the  lantern  microscope,  and  this  one  change  of  the 
conditions  under  which  the  instrument  can  be  used  points 
to  an  improvement  of  no  mean  kind. 

There  are  certain  requirements  to  be  looked  for  in  a 
really  serviceable  lantern  microscope.  The  first  of  them  is 
good  illumination.  The  most  perfect  form  of  limelight  jet 
must  therefore  be  used,  and  even  this,  when  the  higher 


THE  "BOOK  OP  THE  LANTERN. 


241 


powers  of  the  instrument  are  employed,  is  far  from  being 
enough.  The  electric  light  would  obviously  be  the  best 
form  of  illuminant  to  use  for  the  microscope,  but  tlie 
incandescent  variety  is  far  too  feeble,  and  the  arc  form 
possesses  neither  the  steadiness  nor  the  accuracy  and  per- 
manence of  centreing  which  is  so  requisite  in  microscopic 
work.  So  to  the  limelight  we  must  at  present  confine  our 
attention,  aiding  it  as  far  as  possible  by  careful  arrange- 
ment of  the  lenses  used  in  conjunction  with  it.  Hence  the 
condenser  must  be  of  the  best  form,  and  must  be  seconded 
by  a  substage  condenser  suited  to  the  objective  or  power 
which  happens  to  be  used.  Provision  must  also  be  made 
to  filter  the  light  through  a  layer  of  alum  solution,  which 
absorbs  the  heat  rays,  and  saves  valuable  objects  from 
being  destroyed. 

Having  secured  the  brightest  light  possible,  and  done 
our  best  to  concentrate  it  upon  the  object,  we  have 
next  to  consider  the  best  means  of  forming  an  image  of 
that  object  upon  the  screen.  An  objective  may  do  excellent 
work  with  the  ordinary  microscope,  but  utterly  fails  to 
give  a  satisfactory  image  on  the  lantern  screen.  Perhaps  the 
definition  in  the  centre  of  the  disc  is  satisfactory,  but  the 
margins  are  all  hazy  and  indistinct.  One  may  examine  a 
large  numberof  objectives  with  the  lantern  microscope  before 
one  is  found  suited  to  the  work.  But  makers  are  now 
giving  serious  attention  to  the  requirements  of  the  recently 
perfected  instrument,  and  objectives  of  great  excellence 
can  be  obtained. 

One  of  the  most  perfect  as  well  as  simple  arrangements 
for  showing  microscopic  objects  with  the  ordinary  lantern 

R 


242 


THE  BOOK  OF  THE  LANTERN. 


is  the  attachment  shown  at  fig.  61.  This  contrivance 
may  be  compared  to  an  ordinary  microscope  with  its  tube 
removed,  and  with  the  lantern  light  at  the  back  of  the 


Fig.  61. 


stage  instead  of  the  mirror.  The  attachment  is  fixed 
on  the  lantern  in  place  of  the  nsnal  objective,  and  the 
objects  to  be  shown  are  supported  in  a  vertical  position  by 
spring  clips.  The  microscope  objective  is  held,  as  shown, 
on  a  movable  arm  worked  to  and  fro  by  a  milled  headed 
focussing  screw.  At  the  back  of  the  object  is  a  substage 
condenser,  not  shown  in  the  cut,  and  a  revolving  plate 
with  different  sized  diaphragms.  A  trough  containing  a 
saturated  solution  of  alum  is  placed  on  the  lantern  stage 
to  protect  the  objectives  from  heat.  In  using  the  instru- 
ment the  limelight  must  be  adjusted  in  distance  from  the 
condensing  lens  for  each  different  power  used;  and,  indeed, 
for  every  change  in  the  diameter  of  the  diaphragm 
employed.  For  living  objects,  such  as  those  illustrating 
pond  life,  a  small  tank  is  used,  and  is  placed  against 
the  spring  clips  The  objectives  suitable  for  this  form 
of   instrument  are   those  which  range    between    3  in. 


THE  BOOK  OF  THE  LANTERN. 


243 


and  4-10ths  of  an  inch.  Its  performance  leaves  little  to  be 
desired. 

A  far  more  elaborate  form  of  lantern  microscope  is  that 
which  is  shown  at  fig.  62,  and  which  has  been  designed 
by  Mr.  Lewis  Wright.  In  the  opinion  of  most  of  our 
eminent  microscopists,  including  Dr.  Dallinger  and  the  late 
Dr.  Carpenter,  this  instrument  is  by  far  the  most  perfect 
of  the  kind  ever  produced.  Tt  is  certain  that  no  better 
effects  are  possible  than  are  produced  with  high-power 


Fig.  62. 


objectives  with  this  microscope,  until  the  electric  light 
may  be  so  perfected  as  to  place  a  new  power  in  our  hands. 
A  flea  15  feet  long,  literally  larger  than  an  elephant,  is 
shown  with  this  microscope  brilliantly  and  exquisitely 
defined,  while  the  circulation  of  the  blood  in  a  frog's  foot 
can  be  as  easily  seen  as  by  the  table  microscope. 

r  2 


244  THE  BOOK  OF  THE  LANTERN. 

The  instrument  can  be  made  either  complete  in  itself,  as 
shown  in  the  cue,  or  it  can  be  fitted  to  any  good  optical 
lantern.  In  the  first  case,  it  is  provided  with  a  triple  5-in. 
condenser,  which  insures  the  maximum  amount  of  light, 
and  in  the  latter  case  the  lantern  condenser,  of  whatever 
form  it  may  happen  to  be,  is  brought  into  use.  The 
illustration  gives  a  very  fair  idea  of  this  instrument,  by 
which  the  relation  of  its  various  parts  can  be  well  under- 
stood. It  has  a  coarse  adjustment  focussing  screw,  as 
well  as  one  for  fine  adjustment.  The  tube  in  front  of  the 
objective  is  for  the  reception  of  various  lenses  to  give 
extra  amplification,  and  the  necessary  alum-tank  is  let 
into  the  brass  front  tube,  midway  between  its  supporting 
pillar  and  the  large  condensers.  The  details  of  the  stage 
and  revolving  diaphragm  plate  are  much  the  same  as  in 
the  instrument  last  described,  but  the  substage  condensers 
are  of  varying  foci,  and  are  suited  to  the  different  objec- 
tives employed.  The  milled  head  immediately  above  the 
pillar  is  in  connection  with  a  rack  tube,  which  provides  the 
necessary  distance  adjustment  for  these  condensers. 

THE  OPAQUE  LANTERN, 

It  will  be  at  once  conceded  that  most  objects,  animate 
and  inanimate,  can  be  photographed,  and  that  such  photo- 
graphs can  be  used  as  lantern  pictures.  But  there  are 
still  others  which  cannot  be  so  treated,  or  rather,  which 
can  be  better  shown  as  opaque  objects.  The  worker  with 
the  microscope  will  be  able  to  appreciate  the  possibility 
of  showing,  by  means  of  the  lantern,  objects  which  are 
not  transparent.     Some  of   the  most  beautiful  effects 


THE  BOOK  OF  THE  LANTERN. 


245 


seen  in  the  microscope  are  by  means  of  opaque  objects 
viewed  by  means  of  the  spot  lens.  In  like  manner  we 
can  obtain  wonderful  effects  by  the  use  of  the  opaque  lan- 
tern. Let  me  give  one  or  two  examples  of  the  use  of  such 
an  instrument.  Suppose  that  a  lecture  upon  the  history 
and  construction  of  the  watch  is  contemplated.  How  dull 
such  a  lecture  would  be  if  illustrated  merely  by  a  set  of 
diagrams  !  The  audience  would  soon  be  lost  in  the  maze 
of  toothed  wheels  and  springs,  and  few  would  understand 
the  difference  between  one  movement  and  another.  But  let 
the  same  lecture  be  illustrated  by  watches  in*action,  their 
enlarged  images  thrown  on  the  screen,  and  their  wheels  all 
at  work,  and  how  differently  will  the  audience  regard  the 
subject  before  them.  Every  tiny  screw,  the  brilliant  blue 
of  the  steel  parts,  the  very  grain  of  the  metal  is  beauti- 
fully shown,  while  the  ceaseless  and  silent  working  of  the 
mechanism  adds  greatly  to  the  picture.  Coins  and  medals 
can  also  be  splendidly  shown  by  the  same  apparatus,  and 
far  better  than  in  any  other  way.  Various  fruits  can  be 
shown  in  section  ;  a  lemon  or  orange  so  treated  being  a  very 
curious  object,  especially  if  it  be  squeezed,  when  the  pips 
and  juice  fly  upward,  or,  at  any  rate,  appear  to  do  so.  A 
freshly-opened  oyster  makes  another  peculiar  object  for 
the  opaque  lantern.  These  few  examples  will  show  that 
this  form  of  lantern  is  one  which  can  be  of  great  use  in 
intelligent  hands.  It  is  especially  serviceable  to  the 
owners  of  cabinets  or  collections  of  curiosities, — moths  and 
butterflies,  coins,  medals,  shells,  minerals,  &c, — which 
cannot  readily  be  photographed,  or  which  it  is  desirable  to 
show  with  their  natural  colouring. 


246 


THE  BOOK  OF  THE  LANTERN. 


The  opaque  lantern  was  first  devised  by  Chadburn,  and 
for  a  long  time  was  known  by  his  name.  Its  construction 
is  simple  enough.  The  object  is  so  placed  that  it  can  be 
strongly  illuminated  by  the  condensed  rays  from  either 


shown.  At  one  time,  a  large  instrument  of  this  type  was 
made  for  casting  the  image  of  a  human  face  on  the  screen, 
the  lenses  being  of  immense  size.  I  saw  this  instrument 
at  work  more  than  once,  but  its  effect  was  most  dis- 
appointing. It  certainly  was  not  worth  the  trouble  and 
expense  incurred  in  its  construction.  It  was,  of  course, 
fitted  with  a  reversing  lens,  so  that  the  face  should  appear 
the  right  way  up.  The  owner  of  this  face,  by  the  way, 
suffered  tortures  during  the  short  time  of  exhibition,  for 
the  powerful  limelights  close  to,  and  on  each  side  of  his 
head,  were  so  hot  that  they  blistered  his  skin.  He  was 
made  to  smile  at  the  audience,  and  then  to  drink  their 
good  health  in  a  glass  of  wine,  a  refreshment  which  the 
poor  man  really  needed  after  his  grilling. 

Under  the  name  of  Aphengescope  a  contrivance  is  now 
made  for  fitting  on  to  the  ordinary  form  of  lantern,  thus 
dispensing  "with  the  cost  of  extra  lenses.    With  a  lantern 


Fig.  63. 


one  or  two  limelights ;  an  objec- 
tive lens  being  used  to  form  the 
image  on  the  distant  screen. 
The  annexed  diagram,  fig.  63, 
will  explain  the  relations  of  the 
different  parts  of  a  good  opaque 
lantern.  LL  are  the  limelights, 
CC  the  condensers,  O  the  ob- 
jective, and  E  the  object  to  be 


THE  BOOK  OF  THE  LANTERN. 


247 


thus  fitted  ordinary  carte  de  visite  portraits  can  be  shown, 
as  well  as  the  objects  already  enumerated.    Fig.  64  shows 


Fig.  64. 

a  modified  form  of  aphengescope  fitted  to  a  lantern  which 
at  the  same  time  is  ready  to  show  slides  in  the  ordinary 


248 


THE  BOOK  OF  THE  LANTERN. 


manner.  It  will  be  noticed  that  behind  the  objective  is 
placed  a  sloping  mirror,  which  reflects  the  light  upon  the 
card,  photograph,  or  other  object  above  it.  The  objective 
is  then  shifted  from  its  nsnal  position  to  an  orifice  above, 
which  is  shown  in  the  cut  with  a  stopper  in  it.  This 
lantern — the  design  of  Laverne  &  Co. — is  lighted  by  a 
mineral  oil-lamp,  but,  obviously,  the  limelight  could  be 
adapted  to  it.  Mr.  Medland,  of  the  Borough,  has  intro- 
duced a  lantern  on  the  same  principle,  see  fig.  65.    So  much 


Fig.  65. 

light  is  necessarily  absorbed  by  the  arrangements  of  the 
opaque  lantern,  even  in  its  best  forms,  that  the  brightest 
of  illuminants  must  be  secured  to  give  it  full  effect. 
It  is  on  record  that  some  years  back  a  form  of  opaque 


THE  BOOK  OP  THE  LANTERN. 


249 


lantern  was  used  in  an  American  Law  Court  to  demon- 
strate to  a  jury  the  manner  in  which  a  document  had  been 
tampered  with  by  a  forger.  Illuminated  by  a  strong  side 
light,  the  magnified  image  showed  clearly  where  the  tex- 
ture of  the  paper  had  been  disturbed,  both  by  erasure  and 
by  the  action  of  chemicals. 


CHAPTER  XVIII. 


LANTERN  ACCESSORIES. 


CARRIERS. 

LANTERN,  as  supplied  by  the  dealers,  is  with- 
out any  means  of  holding  the  slides  during 
exhibition.  The  slide  stage  is  there,  but  it  is 
about  4^  inches  in  height,  while  the  slides  themselves 
are  3^  inches  square.  To  obviate  this  difficulty,  it 
becomes  necessary  to  fit  this  stage  with  a  wooden 
contrivance  called  a  slide  carrier,  which  can  be  pur- 
chased of  many  different  patterns.  Professional  exhi- 
bitors use  a  wooden  frame  for  each  separate  slide,  but 
this  plan  is  both  inconvenient  and  unnecessary  for  the 
amateur.  Besides  which  it  is  positively  a  bad  plan  for  the 
user  of  a  single  lantern ;  for  as  each  picture  is  removed, 
and  another  one  put  in  its  place,  the  screen  is  left  bare 
while  the  transfer  is  effected.    This  not  only  has  a  bad 


THE  BOOK  OF  THE  LANTERN. 


251 


effect,  but  it  is  distracting  to  the  audience.  Moreover,  the 
pictures  suffer,  for  they  compare  disadvantageously 
with  the  far  brighter  white  disc  by  which  they  are 
alternated. 

I  can  recommend  two  forms  of  carrier  which  obviate 
this  difficulty.  The  first  is  a  grooved  frame,  open  at  either 
side,  with  a  travelling  tape  in  the  lower  groove,  which  is 
put  in  motion  by  a  winch  handle.  The  slides  move 
through  the  lantern  one  after  another,  like  a  panorama, 
but  care  must  be  taken  that  they  are  not  allowed  to  fall 
out  and  get  broken  as  their  time  for  exhibition  expires. 
The  other  form  which  I  recommend  is  quite  different  in 
principle,  and  of  the  two  methods  I  prefer  it.  In  this 
latter  carrier  there  is  a  kind  of  central  frame  which 
is  accurately  adjusted  to  the  lantern  stage.  Within  it, 
and  moving  freely  from  right  to  left,  is  a  double  carrier, 
holding  two  pictures  side  by  side.  While  one  picture 
is  being  shown,  the  other  is  being  changed,  the  right 
and  left  hand  carrier  being  used  alternately.  The  sole 
objection  to  this  form  of  carrier  is  the  necessity  for 
the  exhibitor  to  reach  over  his  lantern  so  as  to  change 
every  other  picture,  which  is  a  slightly  awkward  thing  to 
perform. 

A  modification  of  this  sliding  principle,  which  consists 
of  a  double  changing  stage,  working  vertically,  has  been 
introduced,  but  I  fancy  that  the  lantern  must  be  con- 
structed purposely  for  it.  I  mean  that  it  is  not  sold  as  an 
independent  carrier,  which  can  be  fitted  to  any  existing 
lantern.  This  consideration,  of  course,  greatly  limits  its 
adoption. 


252 


THE  BOOK  OF  THE  LANTERN. 


Whiting's  patent  arrangement  for  facilitating  the  ex- 
hibition of  slides  is  extremely  ingenious,  bnt  seems  to  me 
to  be  an  adaptation  of  Samuels'  changing  box,  for  photo- 
graphic cameras.  At  any  rate,  the  same  principle  is 
involved.  It  consists  of  a  pusher  of  wood  working  be- 
tween grooves  on  the  lantern  stage.  Close  against  it  is  a 
box  of  slides  with  a  powerful  spring  at  the  back  of  them, 
so  that  they  are  forced  up  against  the  pusher,  the  front 
one  being  always  in  the  right  position  to  be  pushed  for- 
ward on  to  the  stage.  The  act  of  moving  the  pusher 
sends  a  picture  on  to  the  stage,  removes  that  previously 
shown,  which  goes  into  another  box,  or  drops  down  an 
inclined  plane  out  of  the  way,  and  at  the  same  time  the 
lens  is  covered  so  that  there  is  momentary  darkness  on 
the  sheet.  This  darkness  is,  I  think,  preferable,  and  less 
trying  to  the  eyes  of  the  audience  than  if  the  actual 
change  of  picture  took  place  visibly. 

Other  forms  of  carriers  provide  in  a  different  manner 
for  the  lens  being  covered  at  the  moment  of  change.  One 
very  good  one  consists  of  a  pair  of  wings,  which  open  and 
close  automatically  over  the  front  of  the  objective  lens 
as  the  change  is  made.  In  this  case  the  first  picture 
seems  to  darken  down  on  the  screen  towards  the  centre, 
the  reverse  action  immediately  discovering  the  nex^ 
slide. 

The  following  remarks,  which  were  written  by  me,  and 
were  published  in  the  Yearbook  of  Photography,  will 
describe  the  kind  of  carrier  which  I  myself  use  :  "  When 
a  man  is  in  the  habit  of  travelling  about  from  place  to 
place  on  lecturing  inteix^, '  ne  will,  if  wise,  reduce  his 


THE  BOOK  OF  THE  LANTERN. 


253 


impedimenta  in  the  shape  of  lantern  and  lantern  belongings 
to  the  smallest  possible  bnlk  consistent  with  efficient  work. 
As  much  of  my  time  has  been  and  is  spent  in  this  way, 
I  have  given  a  great  deal  of  thought  to  this  matter  of 
reduction  of  bulk,  aud  have  achieved  some  little  success  in 
it.  But  it  is  only  to  one  particular  point  that  I  now  wish 
to  draw  attention,  and  I  do  so  in  the  hope  that  what  I  have 
done  may  be  as  useful  to  others  as  it  has  been  to  me.  In 
the  first  place  I  think  that  all  lecturers  will  agree  that  each 
lantern  picture  should  be  fitted  in  a  carrier  of  its  own.  The 
various  forms  of  panoramic  and  shifting  carriers  which  are 
fixed  in  the  lantern  while  the  glass  pictures  are  passed 
through  them  at  the  time  of  exhibition  are  all  very  well 
for  home  use  and  private  work,  but  in  my  opinion  are  not 
suitable  for  employment  in  public  halls.  I  need  not  name 
all  my  objections  to  them,  for  one  will  suffice.  The 
pictures  are  not  sufficiently  protected  from  breakage,  and 
the  risk  of  breakage,  even  of  one  slide  out  of  a  set,  is  a 
thing  not  to  be  thought  of  by  a  good  exhibitor.  At  first  I 
used  7  by  4  mahogany-grooved  carriers  for  all  my  pictures, 
but  I  found  that  they  were  objectionable,  on  two  grounds : 
one  of  these  is  that  they  readily  break,  and  the  other  is 
that  in  packing  they  take  up  far  too  much  room.  It  was 
to  obviate  these  difficulties  that  I  designed  the  carrier  now 
to  be  described,  and  which  I  have  had  in  constant  use  for 
three  years  with  every  success.  My  only  objection  to  it  is 
the  necessity  for  making  it  myself,  which  is  perhaps  no 
real  objection  at  all,  for  a  little  carpentry  forms  a  healthy 
relaxation  to  one  whose  occupations  are  chiefly  of  a  seden- 
tary nature. 


254 


THE  BOOK  OF  THE  LANTERN. 


My  slide-carrier  consists  of  a  piece  of  wood  7  inches  long 
and  4  inches  wide,  with  a  square  opening  in  the  centre  to 
receive  the  glass  picture  of  the  standard  size,  3^  by 
inches.  This  is  faced  on  each  side  with  a  piece  of  card- 
board, the  opening  of  which  is  so  much  smaller  as  to  form 
a  rebate  in  which  the  picture  rests,  and  from  which  it 
cannot  fall  out. 

And  now  to  describe  the  method  of  manufacture.  First 
procure  two  pieces  of  sheet  zinc,  each  measuring  7  by  4  inches 
outside,  but  having  openings  of  slightly  different  areas. 
These  are  indicated  in  the  annexed  cut  (fig.  66),  the  opening 


 ~  — i 

 |i 

I 

 J*  ! 

**  " 1 


L  J 


Fig.  66. 

in  one  piece  of  zinc  being  shown  by  unbroken  lines,  and  in 
the  other  by  dotted  lines.  It  is  best  to  make  these  patterns, 
in  the  first  instance,  in  thin  card,  and  to  hand  them  to  a  good 
workman  to  copy  in  zinc.  (I  may  mention  in  parenthesis 
that  here  I  found  my  chief  difficulty.  The  average  British 
working  man  who  has  been  brought  up  in  the  zinc  industry 


THE  BOOK  OF  THE  LANTERN. 


255 


can  make  a  first-rate  chimney -pot,  but  when  out  of  the 
chimney-pot  groove  he  is  rather  at  sea.  If  he  tells  yon  that  he 
can  cnt  ont  in  zinc  yonr  pattern  correctly,  "  Trnst  him  not, 
lib's  fooling  thee  " ;  at  any  rate,  carefully  check  his  work,  and 
yon  may  find  it  out  a  trifle,  and  this  trifle  when  magnified 
in  the  lantern  is  no  trifle.)  With  correctly-cnt  zinc  patterns 
yon  can  get  through  the  work  of  making  carriers  very 
quickly.  The  pattern  with  the  larger  opening  may  be 
labelled  W,  for  it  is  for  wood  only,  and  the  other  labelled 
C,  for  cardboard. 

The  wood  to  use  is  the  best  pine,  which  in  thickness 
should  approximate  to  the  average  lantern  slide,  say  one- 
eighth  of  an  inch.  This  can  be  obtained  at  any  good  saw- 
mills. Laying  the  zinc  pattern  on  this,  and  pencilling 
*by  its  aid,  a  whole  board  can  be  quickly  marked  out  for 
cutting.  This  cutting  can  be  easily  accomplished  by  using 
a  sharp  shoemaker's  knife.  The  cardboard  can  be  of  the 
thinnest  description,  and  this,  too,  can  be  cut  in  the  same 
manner,  using  the  zinc  pattern  designed  for  it.  With 
several  wooden  pieces  ready  cat,  and  double  their  number 
of  cards,  you  may  now  proceed  to  put  them  together.  With 
good  hot,  but  thin  glue,  paint  over  one  surface  of  the  wood, 
and  press  one  of  the  cards  upon  it,  taking  care  that  the 
centres  of  the  two  agree.  Place  the  joined  pieces  on  your 
work-table,  with  a  heavy,  flat  weight  above  them ;  when 
No.  2  is  similarly,  treated,  place  it  also  under  the  weight,  until 
you  have  a  goodly  pile  of  pieces  of  wood  faced  on  one  side 
with  card.  Leave  them  for  the  night.  The  next  opera- 
tion is  to  place  a  glass  picture  in  each  half-formed  slide, 
and  to  glue  the  cardboard  face  to  each.    Once  more  the 


256 


THE  BOOK  OF  THE  LANTERN. 


hot  glue  and  weight  operation  must  be  repeated,  until  the 
batch, — say  two  dozen  slides,  —is  complete.  When  com- 
plete, this  batch,  with  a  piece  of  blank  board  at  each  end 
of  the  pile,  may  be  screwed  up  between  a  couple  of  car- 
penter's cramps,  and  left  before  the  kitchen  fire  all  day  or 
all  night,  until  the  glue  is  thoroughly  hardened.  When 
quite  dry  and  hard  the  slides  may  be  separate  1  and  again 
arranged  between  the  cramps,  in  such  a  position  that  their 
edges  can  be  run  over  with  a  sharp  plane.  After  this  thev 
can  be  separately  rubbed  on  every  edge  with  glass  paper, 
and,  when  dusted,  they  are  finished. 

The  advantages  of  these  carriers  are  many.  Firstly, 
you  may  drop  one  from  a  height  of  6  feet  from  the  floor 
with  absolute  impunity.  Secondly,  if  the  zinc  patterns 
be  correctly  cut,  the  slides  will  register  correctly  with  one 
another.  Thirdly,  six  dozen, — which  is  about  the  usual 
complement  for  a  lecture  set, — will  pack  in  the  space 
occupied  by  three  dozen  under  the  old  system.  The  sole 
disadvantage  pertaining  to  these  carriers  is,  that  the  pic- 
tures cannot  be  readily  shifted  from  one  to  another.  The 
remedy  is  obvious.  For  lectures  of  an  ephemeral  cha- 
racter,— I  mean  for  those  the  subject  of  which  is  merely 
of  passing  interest, — use  the  old  form  of  carrier,  but  for 
more  permanent  ones  adopt  mine. 

LANTERN  LEGS. 

It  is  given  to  a  few  to  know  what  it  is  to  arrive  at  a 
schoolroom  or  other  lecture-hall  in  some  remote  country 
district,  and  to  expect  to  find  a  few  conveniences  ready  to 
hand.    The  first  thing  to  ask  for  is  a  table,  upon  which 


THE  BOOK  OP  THE  LANTERN. 


257 


can  be  placed  the  lantern-box,  while  the  lantern  itself  com- 
monly screws  to  the  top  of  the  said  box.  There  is  always 
a  difficulty  in  finding  the  right  kind  of  table.  It  is  either 
too  small  or  too  large,  or  else  it  is  rickety  and  nnsafe,  or 
perhaps  it  is  too  beantiful  to  be  devoted  to  such  a  heathen- 
ish purpose  as  the  support  of  a  lantern -box, — all  which 
things  happened  to  me  and  my  assistant  times  out  of 
number,  until  I  invented  a  lantern-support  for  myself, 
consisting  of  four  iron  legs.  With  them  I  can  now  laugh 
the  decrepit  local  table  to  scorn,  and  the  beauty  of  the 
leather-covered  library  specimen,  which  must  not  be 
touched  by  sacrilegious  hands,  is  a  thing  which  ceases  to 
interest  me.  In  a  word,  I  am  independent  of  such  primi- 
tive supports,  and  am  as  proud  of  my  iron  legs  as  is  a 
Chelsea  pensioner  of  the  wooden  understandings  which  he 
exchanged  in  the  Crimea  for  those  with  which  he  was 
born. 

The  accompanying  sketches  will  in  a  moment  cause  the 
form  and  purpose  of  these  legs  to  be  understood.  They 
are  made  of  iron,  having  a  sectional  area  of  1  inch  by 
three-eighths  of  an  inch.  Each  fits  into  a  socket  upon  the 
lantern  box,  and  each  has  at  its  lower  end  a  kind  of  flat 
toe  turned  outwards,  through  which  is  a  hole  by  which 
the  leg  can  be  screwed  to  the  floor.  This,  however,  is 
hardly  necessary,  for  the  weight  of  the  lantern  and  its 
box,  together  with  the  slides  which  it  .contains  whilst  in 
use,  are  quite  sufficient  to  make  the  whole  arrangement  as 
firm  as  a  rock. 

In  the  annexed  cut  (fig.  67)  A  is  the  lantern  box,  fitted  with 
a  strong  frame  at  the  bottom,  F,  upon  which  the  sockets  can 

S 


258 


THE   BOOK  OF  THE  LANTERX. 


be  screwed.  L  is  one  of  the  legs  in  position.  T  is  an 
enlarged  view  of  the  toe  of  one  leg,  showing  the  screw- 
hole  where  it  can  be  attached  to  the  floor.     A1  is  a  socket, 


Fig.  67. 


showing  how  it  is  composed  of  two  pieces  of  iron,  one  flat 
and  one  bent.  I  may  mention  that  the  top  of  the  leg, 
which  fits  into  the  socket,  is  diminished  in  size  for  that 
purpose,  and  that  the  shonlder  thns  formed  on  it  holds  it 
firmly  in  position.  I  have  used  these  legs  for  several 
years,  and  have  never  seen  anything  which  would  fulfil 
their  purpose  so  well.  They  can  be  secured  for  travelling 
by  a  couple  of  leather  straps,  or  can  be  made  to  go  inside 
the  lantern-box.  Their  combined  weight  is  fourteen 
pounds. 


THE  BOOK  OF  THE  LANTERN. 


259 


HAND  CAMERAS. 

Photographic  negatives  for  lantern  slides  should  be 
rather  less  dense  than  those  used  for  ordinary  printing 
upon  paper  :  hence  it  is  better  to  take  uegatives  for  the 
purpose  than  to  utilise  others  which  have  been  taken  for 
ordinary  reproduction.  The  lesser  density  must  be  gained 
by  stopping  the  development  judiciously,  and  not,  of 
course,  by  checking  the  exposure.  There  are  many 
cameras  now  to  be  had  which  take  small  negatives  suitable 
for  lantern  work.    These  are  so  compact  and  self-contained 


Fig  68. 


that  they  require  no  stand,  focussing-cloth,  or  other  adjunct 
and  will  readily  pack  away  in  a  portmanteau  or  box 
without  inconvenience  to  the  traveller.  The  author  has 
used  a  camera  of  this  description  with  great  advantage,  and 
has  taken  many  dozens  of  instantaneous  pictures  with  it. 

A  useful  form  of  hand-camera  introduced  by  the 
Stereoscopic  Company  is  here  shown  (see  fig.  68). 

s  2 


260 


THE  BOOK  OF  THE  LANTEliN. 


Another  camera  which  is  made  purposely  for  lantern- 
slide  negative  making  has  been  recently  introduced  by 
Messrs.  May  field  &  Cobb.  This  will,  when  folded  np,  easily 
go  into  the  pocket,  and  is  nsed  like  the  last-described 
whilst  held  in  the  hand  (see  fig.  69). 


Fig.  69. 


A  great  deal  of  attention  has  lately  been  aroused  with 
respect  to  so-called  detective  cameras.  They  would  perhaps 
be  better  described  as  concealed  cameras,  for  there  are  many 
reasons  why  they  cannot,  except  by  some  happy  conjunc- 
tion of  circumstances,  be  used  in  the  detection  of  crime. 
Their  manufacture  has  certainly  been  brought  to  great 
perfection,  and  a  wonderful  amount  of  ingenuity  has  been 
displayed  in  their  construction.  From  experience  I  can 
speak  most  highly  of  the  good  pictures  which  can  be  pro- 
duced by  them.  But  one  essential  condition  must  not  be 
absent ;  such  pictures  want  absolute  sunshine.  I  give 
three  examples  of  these  detective  cameras.  The  first, 
Watson's  (fig.  68),  is  a  leather-covered  box,  containing  as 


THE  BOOK  OF  THE  LANTERN. 


261 


will  be  seen  oy  the  dotted  lines,  a  complete  camera.  This 
camera  can  be  focussed  and  manipulated  altogether  by 
touching  buttons  on  the  outside  of  the  box. 


Fig.  70. 


Next  I  notice  Marion's  Parcel  Camera  (fig.  71),  which 
is  of  different  construction  altogether.  It  consists  of  a 
covered  box,  like  a  parcel,  but  this  box  forms  the  camera 
with  a  lens  in  front  concealed  by  a  paper  flap.  The 


Fig.  71. 

illustration  shows  the  appearance  of  the  underside  of  the 
box,  with  a  slit  at  one  end  for  the  reception  of  the  sensitive 
plate  and  the  instantaneous  shutter  apparatus  at  the  other 
end.    The  plate  is  contained  in  a  bag  of  the  shape  shown 


262  THE  BOOK  OF  THE  LANTERN 

at  fig.  72,  which  locks  on  to  the  aperture  in  the  bottom  of 
the  box,  when  a  plate  has  to  be  transferred  from  one 
to  the  other.  I  have  found  both  these  cameras  to  work 
perfectly. 


Fig.  72. 


The  newest  arrangement  of  the  kind  is  the  Kodak 
Camera  introduced  by  the  Eastman  Company  (see  fig.  72). 
In  this  small  box  a  hundred  pictures  can  be  taken  by 
the  simplest  possible  movements.  It  contains  a  ribbon 
of  sensitive  material,  which  is  used  panorama  fashion 
instead  of  glass  plates. 


Fig.  73. 


I  am  convinced  that  there  is  a  very  great  future  before 
these  detective  or  concealed  cameras.  That  they  will  pro- 
duce negatives  of  firstrdass  quality,  I  have  proved  again 


THE  BOOK  OF  THE  LANTERN. 


263 


and  again,  and  it  is  the  thought  that  such  negatives  can  be 
so  readily  made  to  give  lantern  slides,  or  can  be  used  for 
enlarging  purposes  with  the  help  of  the  lantern,  which  has 
induced  me  to  give  this  brief  notice  of  them  in  my  chapter 
on  lantern  accessories. 


CHAPTER  XIX. 


PRACTICAL  HINTS  TO  THOSE  WHO  EMPLOY  THE  LANTERN  FOR 
SCIENTIFIC  DEMONSTRATION,  OR  FOR  ENTERTAINMENTS  IN 
THE  DRAWING-ROOM  OR  LECTURE-HALL. 


IN  the  foregoing  pages  I  have  endeavoured  to 
describe  the  best  methods  of  manipulating  the 
lantern  ;  and  I  hope  that  I  have  done  so  in  such 
a  manner  as  to  enable  all  my  readers  readily  to  under- 
stand the  working  of  this  beautiful  instrument.  I  feel 
convinced  that  if  my  instructions  are  carefully  followed 
all  will  go  well, — at  all  events,  in  the  apparatus  depart- 
ment. But  the  best  instrument  is  no  good  unless  the 
lecturer  be  an  efficient  showman  and  speaker.  Unfor- 
tunately many  essay  the  task  of  lecturing  who  are  physi- 
cally unfit  for  it.  There  are  many  good-natured  people  in 
the  world  who  will  undertake,  very  often  for  some  charity, 
to  act  as  lecturer  in  a  school-room,  the  slides  being 
borrowed  from  some  optician  with  a  printed  lecture  fitted 
to  them.  This  good-natured  man  will  take  up  the  work 
without  much  thought  or  consideration,  and  the  result  is 
too  often  a  very  bungling  performance.    A  man  may  have 


THE  BOOK  OF  THE  LANTERN. 


265 


a  fund  of  knowledge,  but  lack  the  power  of  imparting  it  to 
others.  The  fault  is  common  enough  in  the  pulpit,  where 
it  is  often  the  case  that  a  clergyman  who  has  won  high 
honours  at  the  university,  and  as  a  reward  for  his  scholar- 
ship finds  himself  in  due  course  incumbent  of  a  living,  is 
an  utterly  incapable  speaker,  greatly  to  the  distress  of  his 
congregation.  He  can  of  course  compile  or  write  a  good 
sermon ;  that  is  to  say,  a  discourse  which  is  carefully  con- 
structed and  perfect  as  a  specimen  of  written  English  ;  but 
when  he  gets  into  the  pulpit  he  reads  it  out  in  such  a 
droning  voice,  and  with  such  a  lack  of  emphasis,  that  many 
of  the  congregation  dose  off  into  peaceful  slumber.  Many 
lecturers  have  the  same  want  of  ability,  and  it  is  this 
circumstance  that  has  had  the  effect  more  than  any  other 
of  prejudicing  people  against  a  lecture,  as  a  thing  which  is 
necessarily  dull  and  the  reverse  of  entertaining. 

More  than  once  it  has  fallen  to  my  lot  to  lecture  in  some 
hall  which  is  strange  to  me,  and  on  such  an  occasion  1  have 
generally  asked  the  hall-keeper  if  a  large  audience  may  be 
reasonably  looked  for.  The  answer  is  too  often  something 
like  this  : — "  Well,  sir,  the  people  hereabouts  don't  much 
care  for  a  lecture  ;  but  last  Saturday  night  the  place  was 
crowded  from  floor  to  ceiling."  "  Dear  me ! "  is  my  answer, 
"  and  who  was  the  lecturer  on  that  occasion  ?  "  "  Lor' 
bless  your  soul,  sir,  it  wasn't  no  lecture,  it  was  niggers."  I 
leave  my  readers  to  imagine  with  what  feelings  I  looked 
forward  to  the  pleasure  of  meeting  my  audience. 

A  lecture  entertainment  will  fail  sometimes  owing  to  the 
total  incapacity  of  the  speaker, — to  his  bad  articulation, 
nervousness,  lack  of  voice,  or  want  of  tact  in  dealing 


266 


THE  BOOK  OF  THE  LANTERN. 


with  the  audience.  Still  more  often  failure  is  due  to  bad 
arrangement  of  the  matter  which  the  lecturer  has  under- 
taken to.  deliver.  The  remedy  for  this  last  fault  is 
obvious,  namely,  a  course  of  training  in  the  reading  of 
standard  works.  Some  may  perhaps  think  I  am  recom- 
mending an  old-fashioned  book,  when  I  name  "  Blair's 
Lectures  on  Rhetoric,"  as  a  very  valuable  aid  to  the  writer 
and  speaker.  I  would  advise  all  beginners  to  write  their 
lectures  and  go  over  the  matter  again  and  again,  before 
trusting  themselves  on  the  platform ;  and  in  constructing 
the  fabric  of  their  discourse,  let  them  remember  that  the 
sentences  should  be  as  a  rule  shorter  than  if  the  words  were 
merely  intended  for  the  eye  of  a  reader.  A  sentence  con- 
sisting of  several  lines  without  any  full  stop,  although  it 
may  pass  in  ordinary  composition,  is  very  tiresome  to  listen 
to  ;  a  most  attentive  audience  will,  by  the  time  the  verbose 
paragraph  ends,  forget  its  opening,  and  the  sense  be 
consequently  lost.  Again,  in  composing  a  lecture  which 
is  illustrated  by  lantern  pictures,  care  must  be  taken  to  so 
arrange  it  that  the  pictures  come  in  naturally,  and  are  not 
dragged  in  willy-nilly,  as  if  they  were  in  stock  and  must  be 
shown  at  any  price.  The  views  should  be  the  best  of  their 
kind,  but  must  be  altogether  subservient  to  the  text.  If  a 
part  of  the  subject  is  of  such  a  nature  that  it  may  be  likely 
to  prove  tedious  to  an  audience, — and  audiences  differ 
amazingly  in  their  receptive  faculties,— that  part  should 
either  be  compressed,  or  it  may  be  lightened  by  a  good  anec- 
dote, or  even  by  some  illustration  which  will  raise  a  laugh. 
Such  pictures  introduced  with  circumspection  are  most 
useful ;  but  the  power  of  employing  them  should  be  used 


THE  BOOK  OF  THE  LANTERN. 


267 


sparingly.  Let  the  lecturer  look  upon  them  as  the  high- 
lights of  a  work  of  art.  The  novice  with  a  brush  will  daub 
such  high-lights  on  every  projecting  corner  of  the  compo- 
sition, until  the  beauty  of  the  whole  is  lost  in  their  glare  ; 
a  true  artist,  on  the  other  hand,  will  deftly  put  in  a  touch 
here  and  another  there,  with  the  result  that  the  whole  work 
is  brightened  and  generally  improved. 

The  grosser  faults  into  which  a  novice  in  lecturing  is 
apt  to  fall  are  generally  the  result  of  simple  inexperience 
or  carelessness.  He  should  make  it  a  golden  rule  that 
whatever  may  occur  he  must  not  lose  his  temper.  In  the 
ordinary  affairs  of  life,  the  man  who  can  control  his  temper 
has  always  the  best  of  an  argument ;  and  still  more  so  is 
this  the  case  on  the  platform  (and  on  this  platform,  let 
us  remember  that  there  are  often  some  very  trying  inci- 
dents to  deal  with,  particularly  amid  the  darkness  of 
lantern  illustrations).  I  once  found  it  very  hard  to  control 
both  my  sentences  and  my  temper,  when  I  became  aware 
that  I  was  a  target  for  some  mischievous  boy's  pea-shooter ; 
but  on  politely  addressing  the  unseen  youth,  and  telling 
him  that  I  knew  he  was  a  very  smallhoy,  and  that  therefore 
I  could  excuse  his  childish  conduct,  but  at  the  same  time  he 
must  keep  his  peas  in  his  pocket,  the  nuisance  stopped.  I 
recently  heard  of  a  case  where  an  inexperienced  lecturer 
was  loudly  told  more  than  once  to  "  speak  up."  Instead  of 
taking  this  invitation  as  a  valuable  hint,  and  acting  upon 
it  as  he  should  have  done,  he  retorted  rudely,  and  the  audi- 
ence refused  to  listen  to  him  any  longer.  It  is  to  be  hoped 
that  he  will  not  again  attempt  work  for  which  he  is 
evidently  quite  unfitted. 


268 


THE  BOOK  OF  THE  LANTERN. 


Iii  lectures  of  a  popular  and  entertaining  character, 
it  is  often  desirable  to  introduce  a  little  music;  but  if 
this  is  done  at  all  it  should  be  done  well,  the  lecturer  first 
of  all  satisfying  himself  as  to  the  capabilities  of  the 
musician.  They  should  then  arrange  together  where  the 
music  is  to  come  in,  and  the  player  should  have  furnished 
to  him  by  the  lecturer  a  set  of  cues,  with  hints  as  to  the 
nature  of  the  music  to  be  played  at  the  occurrence  of  those 
particular  words.  To  show  that  this  precaution  is  not  an 
idle  one,  let  me  state  that  recently  I  heard  a  lecture  de- 
livered in  which  a  few  bars  of  music  came  in  at  stated 
times.  On  one  of  those  occasions  the  lecturer  was  showing 
a  tomb  erected  to  the  memory  of  some  celebrity  who  had 
recently  departed.  He  described  this  tomb  and  said  a  few 
touching  words  with  reference  to  the  high  character  of  the 
departed  one  ;  and,  he  had  no  sooner  finished,  than  the 
pianist  at  his  elbow  struck  up  a  merry  waltz  ! 

The  lecturer  should  be  careful  to  select  an  intelligent 
open  tor.  The  man  employed  should  be  one  capable  of 
concentrating  his  attention  upon  the  work  which  he  has 
to  do.  The  gases  will  require  attention,  the  lime  wants 
turning  every  few  minutes,  or  the  light  from  the  lantern 
soon  drops ;  but,  at  the  same  time,  too  much  should 
not  be  thrown  upon  the  hands  of  the  operator;  for  in- 
stance, the  lecturer*  should  make  it  a  standing  rule  to  go 
carefully  through  the  slides  which  are  to  be  shown  before 
the  lecture  commences,  so  that  each  one  is  not  only  in  its 
proper  place,  but  each  is  so  arranged  that  the  operator  will 
hardly  be  able  to  put  one  in  the  lantern  except  in  its  right 
position.    A  landscape,  or  more  especially  a  portrait,  ap- 


THE  BOOK  OF  THE  LANTERN. 


269 


pearing  suddenly  on  the  sheet  standing  on  its  head,  is  an 
episode  which  disturbs  both  lecturer  and  audience,  and 
will,  for  a  time,  entirely  break  the  thread  of  the  discourse. 
This  can  easily  be  avoided  if  the  slides  be  marked  in  a 
certain  way.  If  the  slides  are  being  used  in  fixed  carriers, 
and  are  therefore  simply' in  the  form  in  which  they  are  sold 
at  the  shops,  each  one  should  be  marked  with  a  white  disc 
at  the  lower  left-hand  corner  of  the  picture,  taking  care 
that  the  wafer  is  on  the  face  of  the  picture,  and  by  pre- 
ference, beneath  the  cover  glass,  so  that  it  cannot  be  rubbed 
off.  This  white  wafer  will  then  come  conveniently  below  the 
operator's  thumb  when  the  slide  is  in  its  inverted  position, 
as  it  should  be,  before  being  placed  in  the  lantern. 
The  operator  will  then  become  accustomed  to  look  for  this 
white  dot,  which  he  can  easily  see  even  in  a  darkened 
room,  and  he  will  place  his  thumb  above  it,  and  the  picture 
will  of  necessity  appear  on  the  sheet,  as  it  should  do.  Tf 
the  back  of  the  picture  is  placed  next  the  light,  of  course 
everything  on  the  sheet  appears  in  reversed  order.  What 
should  be  the  right  hand  of  the  picture  appears  on  the  left 
of  the  sheet,  and  vice  versa.  This  is  of  no  great  conse- 
quence in  some  cases ;  but  if  the  picture  should  include 
any  lettering,  such  as  that  on  a  sign -post  or  a  shop-front, 
these  letters  will  appear  backwards,  and  the  fault  is  at 
once  detected  by  the  audience,  and  commented  on  by  them 
in  audible  whispers.  I  once  had  a  volunteer  assistant  who, 
at  short  notice,  supplied  the  place  of  my  regular  operator, 
who  happened  to  be  ill.  In  the  middle  of  my  lecture  this 
man  showed  a  slide  upside  down  ;  on  seeing  his  mistake, 
he  took  it  out  of  the  lantern  and  put  it  in  again  sideways. 


2  70 


THE   BOOK  OF  THE  LANTERN. 


He  again  saw  the  error,  took  it  out  of  the  lantern,  and  re- 
placed it,  but  on  its  other  side ;  so,  in  reality,  this  genius 
tried  every  conceivable  way  of  showing 
that  picture  but  the  correct  one. 

It  is  imperative  that  there  should  be 
some  well-understood  code  of  signals  be- 
tween the  lecturer  and  the  lantern  operator, 
for.  in  many  cases  they  are  50  feet  apart. 

Some  lecturers  are  content  with  verb;  1 
directions,  but  these  are  simply  intoler- 
able to  any  one  with  any  idea  of  what 
a  lecture  should  be.  To  hear  a  man 
calling  out,  "  Next  picture,  please,"  and 
so  on,  utterly  spoils  even  a  lecture  which 
is  good  in  other  respects.  An  audible 
sound  signal,  such  as  tapping  with  a 
pointer,  or  sounding  a  gong  when  the 
picture  is  required  to  be  changed  is 
almost  as  bad.  A  lecture  lamp  has 
recently  been  introduced,  which  not  only 
comprises  a  shade  light  for  the  lecturer's 
desk,  but  has  at  the  back,  i.e.,  the  side 
presented  towards  the  audience,  and  there- 
fore towards  the  lantern,  a  little  disc  of 
red  glass,  which  is  uncovered  by  touching 
a  lever  at  the  side  of  the  lamp.  See  S, 
.xg.  7 4.  When  the  operator  sees  the  little  red  flame  dis- 
closed he  knows  that  a  fresh  picture  is  wanted,  and  should 
he  be  inattentive  to  that  signal  there  is  a  little  gong,  B,  below 
the  lamp  which  can  be  used  on  such  an  emergency.  This 


Fig.  74. 


THE  BOOK  OF  THE  LANTERN. 


271 


lamp  is  portable,  convenient,  and  efficient.  But  above  all 
devices  for  signalling  I  prefer  a  simple  electric  arrange- 
ment. The  one  that  I  am  in  the  habit  of  using  consists  of 
a  single-stroke  electric  bell  with  the  gong  removed  from  it. 
When  the  current  is  sent  through  the  coils  of  the  attached 
magnet,  the  armature  is  of  course  attracted,  and  a  little 
tap  is  heard,  which,  although  quite  unnoticed  by  the 
audience,  is  easily  heard  by  the  operator,  who  is  on  the 
look  out  for  it.  I  used  to  employ  in  connection  with  the 
bell, — if  bell  it  can  be  called, — a  Leclanche  battery  which 
was  placed  just  below  my  reading-desk.  While  on  the 
desk  itself  I  had  an  ordinary  bell  push,  connected  with 
both  bell  and  battery.  But  this  arrangement  I  have  since 
superseded  by  a  better  one.  The  Equitable  Telephone 
Company  have  brought  out  an  electric  bell  which  is  quite 
independent  of  battery  power,  a  small  magnetic  arrange- 
ment taking  its  place.  This  generator,  as  it  is  called,  is 
shown  at  fig.  75.  It  acts  most  perfectly,  and  is  destined, 
I  should  presume,  to  work  a  revolution  in  electric  bell 
mechanism  generally.  The  only  inconvenience  in  the 
arrangement  is  the  difficulty  that  is  sometimes  found  in 
carrying  the  wires  between  the  lecturer  and  the  lantern, 
and  so  concealing  them  or  putting  them  out  of  reach 
that  there  is  no  chance  of  their  being  tampered  with  by 
mischievous  hands.  In  a  lecture  theatre,  where  there  is 
commonly  a  gallery,  the  wires  can  be  run  round  the 
front  of  the  balcony  quite  out  of  sight.  In  other  cases 
they  can  be  laid  on  the  floor  underneath  the  carpet  or 
matting.  In  nine  cases  out  of  ten  there  is  no  difficulty 
in  adjusting  them.     The  signal  should  be  given  about 


272 


THE  BOOK  OF  THE  LANTERN. 


half  a  minute  before  the  change  of  picture  is  really 
required,  so  as  to  give  the  operator  time  for  the  necessary 
manipulation.  He  should  be  instructed  when  to  dissolve 
the  view  slowly,  should  he  be  using  a  double  or  triple  lan- 
tern, and  when  to  make  the  change  quickly.  To  dissolve  a 
diagram  or  a  portrait  is  ridiculous,  and  sometimes  leads  to 


Fig.  75. 

very  comical  effects.  I  remember  once  attending  a  lecture 
where  a  number  of  illustrations  were  shown  of  different 
types  -  of  national  costumes.  First  of  all  there  came  a 
woman  in  peasant's  dress.  This  was  followed  by  a  man 
whose  lower  extremities  were  clothed  in  tight-fitting  white 
unmentionables.  It  so  happened  that  one  figure  occupied 
on  the  screen  exactly  the  same  place  as  the  other,  so 


THE  BOOK  OF  THE  LANTERN. 


273 


that  when  the  lady  was  slowly  dissolved  into  the  gentle- 
man, the  astounding  effect  was  produced  of  her  clothes 
gradually  melting  from  her  form. 

I  must  now  bring  my  remarks  to  a  conclusion,  with 
the  hope  that  many  will  find  my  book  useful.  If  the 
word  Ego  has  crept  in  with  too  much  persistence,  I  trust 
that  my  indulgent  readers  will  impute  it  rather  to  personal 
acquaintance  with  the  things  of  which  I  write  than  to  any 
less  worthy  source. 


INDEX. 


Advantage  of   pure  hydro- 
gen, 69. 
Aniline  colours,  161. 
A  phengescope,  246. 
Astrometeoroscope,  The,  180. 

Bell,  Electric,  271. 
BiuDial,  Detachable,  13. 
Biunial  lantern,  8. 
Blow-through  jet,  53. 
Boards,  Double,  62. 
Brass  work,  Superfluous,  10. 
Brewster,  Sir  David,  5. 
Brin's  Oxygen  method,  46. 

Cameras,  Detective,  260. 
Camera  for  microscope,  215. 
Cameras,  Hand,  259. 
Capacity  of  cylinders,  49. 
Carriers,  250. 
Cellini,  1. 

Choreutoscope,  The,  180. 


Clamp,  Steward's,  56. 
Clouds,  164. 
Clouds,  Printing,  233. 
Cohesion  figures,  175. 
Collodio-bromide  process  111. 
Colosseum,  1. 
Coloured  gelatine,  188. 
Colouring  lantern  slides,  145. 
Colours,  Complementary,  166, 
188. 

Colours  used  for  slide  painting, 
149. 

Complementary  colours,  166, 
188. 

Compound  frame  for  copying, 
126. 

Compressed  oxygen,  48. 
Condenser,  Dallmeyer's,  23. 
Condensers,  21. 
Copying  apparatus,  124. 
Copying  paper  prints,  121. 
Current  reverser,  173. 


276 


INDEX. 


Cutting  masks,  142. 
Cylinders,  Capacity  of,  49. 
Cylinders  for  gas,  48. 

Dallmeyer's  Condenser,  23. 
Decomposition  of  water,  192. 
Desk  for  slide  painting,  148. 
Detachable  biunial,  13. 
Detective  cameras,  260. 
Developers,  120,  121. 
Development,  119. 
Development  of  photograph  in 

lantern,  199. 
Dissolver,  9,  80. 
Distance  between  lantern  and 

sheet,  95. 
Distances,  Table  of,  96. 
Double  boards,  62. 
Drummond  Light,  5. 
Drying-rack,  136. 
Dry  plate  slides,  109. 

Easel  for  enlarging,  224. 
Electric  Bell,  271. 
Emulsion,  Filtering,  132. 
Emulsion  making,  128. 
Enlarging  lantern,  239. 
Enlarging  photographs,  222. 
Enlargements,  209. 
Equivalent  focus,  95. 
Ether-oxygen  light,  83. 
Experimental  lantern,  190. 
Experiments  with  tank,  193. 
Exposing  gauge,  229. 
Exposure,  117. 

Exposures  for  enlargements, 
228. 


Filtering  Emulsion,  132. 
Frame  for  sheet,  93. 
Frogs'   legs,    Projection  of. 
174. 

Gas-bags,  58. 

Gas  bottles  or  cylinders,  48. 
Gelatine  process,  115. 
Gelatino-bromide  paper,  225. 
Gelatino-chloride  plates,  133. 
Glass  grinding,  101. 
Ground-glass    lantern  slides, 
99. 

Ground-glass  varnish,  102. 
Gauge  for  exposures,  229. 

Hand  Cameras,  259. 
Hanging  the  sheet,  88. 
Hints,  Practical,  2^4. 
Home-made  gelatine  platen 
127. 

Hydrogen  generator,  69. 

Ice  experiment,  197. 
Iceland  Spa,  187. 
Intensifying,  140. 

Jet,  Blow-through,  53. 
Jet,  Mixed,  53. 
Jet,  Oxycalcium,  50. 

Kaleidotrope,  The,  179. 
Kircher,  3. 

Lamp,  Newton's,  6. 
Lantern  and  Photography, 
The,  204. 


INDEX. 


277 


Lantern,  Binnial,  8. 
Lantern  enlarging,  239. 
Lantern  enlargements,  209. 
Lantern  for  experiments,  190 
Lantern,  How  to  work,  76. 
Lantern  le^'S,  256. 
Lantern  microscope,  240. 
Lantern,  Mineral  Oil,  7. 
Lantern,  Opaque,  244. 
Lantern-slides,  97. 
Lantern-slide  colouring,  145. 
Lantern  -  slides    from  paper 

prints,  121. 
Lantern  slides  on  dry  plates, 

109. 

Lantern-slides     on  ground 

glass,  99. 
Lantern-slides  on  wet  plates, 

104. 

Lantern- slides  with  transferro- 

type  paper,  143. 
Lantern,  Triunial,  15. 
Lecture-lamp,  270. 
Lenses,  Condensing,  21,  23. 
Lenses,  Objective,  26,  27. 
Lens,  Supplementary,  22. 
Limes,  71. 
Lime -shield,  57. 
Limes,  Preserving,  74. 

Magnetic  experiments,  201. 
Making  emulsion,  128. 
Making  oxygen,  30 
Masks,  Cutting,  142. 
Micro,  Attachment,  220,  242. 
Microscope,  Camera  for,  215. 
Microscope,  Lantern,  240. 
Mineral  oil  lantern,  7. 


Mixed  jet,  53. 
Mixture,  Oxygen,  40. 
Moonlight  pictures,  159. 
Mounting,  141. 

Newton's  Lamp,  6. 

Oakley's  regulator,  64. 
Objective  lenses,  26,  27. 
Opaque  lantern,  2  14. 
Opaque      lantern,  principle 

of,  2. 
Optical  system,  16. 
Oxycalciurn  jet,  50. 
Oxygen,  Briu's  method,  46. 
Oxygen,  Compressed,  48. 
Oxygen-ether  light,  83. 
Oxygen  making,  30. 
Oxygen  mixture,  40. 
Oxygen  retort,  32. 

Painting  with  aniline  colours, 
161. 

Photographs,  Enlarging,  222. 
Photo-micrographs,  211. 
Portable  fiame,  93. 
Practical  hints,  264. 
Preserving  limes,  74. 
Pressure  boards,  60. 
Primitive  lime-light,  51. 
Printing  clouds,  233. 
Prism,  The,  182. 
Pure  hydrogen,  Advantage  of, 
69. 

Purifier,  or  Wash-bottle,  37. 

Rack,  Washing,  136. 
Regulator,  Oakley's,  64. 
Retort,  Oxygen,  32. 
I 


278 


INDEX. 


Sand  -  glass,   Projection  of, 
175 

Sciopticon,  6 
Screens,  86 
Sheet,  Hanging,  88 
Short-focus  lens,  138 
Signalling,  271 
Simple  regulator,  68 
Sir  David  Brewster,  5 
Sky,  Treatment  of,  139 
Slides  by  contact,  137 
Spectrum  slides,  186 
Steward's  clamp,  56 
Steward's  regulator,  68 
Superfluous  brasswork,  10 
Supplementary  lens,  22 
Support  for  lantern,  256 

Table  of  distances,  96 
Tank  experiments,  193 
Tannin  process,  110 
The  Astrometeoroscope,  180 
The  Choreutoscope,  180 


The  Galvanometer-slide,  171 

The  Kaleidotrope,  179 

The  Prism,  182 

"Toilers    of    the  Thames," 

Frontispiece. 
Treatment  of  sky,  139 
Triunial  dissolrer,  81,  82 
Triunial  lantern,  15 
Tubes,  76 

Tyndall's  ice  experiment,  197 

Use  of  condenser,  18 

Vertical  attachment,  12 
Vortex  rings,  191 

Wash  bottle,  or  purifier,  37 
Water,  Decomposition  of,  192 
Wet  Collodion-slides,  104 
Whitewashed  screen,  91 
Woodbury-type  process,  113 
Working  the  lantern,  76 


READ  WHAT  PROMINENT 

AMATEURS 

SAY  OF  THE 

SUTER  LENS. 

MESSRS.  ALLEN  BROS.  New  York,  February  20,  1889. 

Dear  Sirs  :  You  ask  me  to  give  you  my  opinion  of  the  Suter  Lens 
bought  of  you  three  or  four  years  ago.  It  gives  me  pleasure  to  write 
you  that  it  is  my  favorite  lens  for  out-of-door  work — I  have  eight  of 
various  makes.    It  works  rapidly,  and  has  great  depth  of  focus. 

Yours  very  truly, 

R.  Swain  Gifford. 

MESSRS.  ALLEN  BROS.  New  York,  February  20,  1889. 

Dear  Sirs  :  I  am  glad  to  write  you  that  the  No.  4  B  Suter  Lens, 
which  I  bought  of  you  some  time  ago,  is  very  satisfactory.    It  is  about 

as  quick  as  my          lens,  and  is  very  sharp  focus.    I  use  it  almost 

entirely  in  my  studio.  Yours  very  truly, 

Louis  C.  Tiffany. 


From  t  lie  Balloon  Photographer. 

Messrs.  Allen  Bros.  Winsted,  Ct.,  November  26, 1886. 

Although  circumstances  compelled  me  to  give  up  my  projected  bal- 
loon trip  this  fall,  I  have  used  my  3  A  "  Suter  "  for  other  work,  photos 
of  animals,  viewing,  etc.  I  am  glad  to  say  that  each  time  I  have  used 
it,  it  has  impressed  me  with  a  stronger  sense  of  its  good  qualities. 
With  your  Lens  and  a  Prosch  Duplex  Shutter,  which  is  fitted  to  it,  I 
feel  well  equipped  for  quick  work  and  feel  confident  of  success  in  my 
next  balloon  trip  whenever  that  is. 

Very  respectfully, 

John  G.  Doughty. 

ALLEN  BROTHERS, 

DETROIT,  MICH. 

Sole  Agents  for  the  United  States. 


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S.  HAWK  RIDGE, 

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(  288  ) 


r 


v. 


GETTY  RESEARCH  INSTITUTE 

II 

3  3125  00987  8253 

